On 7 February this year, Giles Duley, an independent 39-year-old British photographer, was blown up by a landmine in Afghanistan. He became a triple amputee, losing his left arm and both legs. His life is a miracle – most soldiers with similar injuries do not survive. It is his suggestion that we meet at London's Charing Cross hospital, where he is recovering from an operation to ease ossification of muscle at the end of one of his leg stumps.

I am not used to combining interviewing with hospital visiting but it is obvious that this is typical Duley. He has stoicism and spark, wants to get on with things, is more than willing to answer questions from his hospital bed. And this is not the half of it. As soon as he is fit enough, he plans to return to Afghanistan to photograph the medical treatment of injured civilians in Kabul. He has it all worked out – even down to the tripod head (his innovation) that will attach to what remains of his left arm and on to which a camera can be affixed: "My friends love this idea of me as half man, half camera," he says and laughs – as if this metamorphosis had always been on the cards.

Our reason for meeting is, in part, Becoming the Story, a retrospective of his work. His pictures are tremendous. He has taken former Unita soldiers in Angola, acid-burn survivors in Bangladesh, a Nuer woman giving birth to a stillborn child (for which he won an award in the Prix de la Photographie, Paris in 2010).

I tell him his images would do nothing to calm the primitive anxiety that photographers steal souls: he has an ability to see through people. And yet what shines out of the work is, above all, his respect for the uniqueness of each human being. He does not see himself as a photojournalist. He is aiming for the "universal". Empathy is his gift. It should be me putting Duley at his ease – but it is the other way round. He looks alert and owlish in his specs but is easy, bright and talkative. His girlfriend, Jen, is at his bedside and we chat about the marathon she is running to raise money for him, then she heads off to the canteen, promising to be back soon.

Duley returns toAfghanistan as soon as she has gone – as he must repeatedly in his own mind; it is the story that has to be told in order to move on. He was with the 1st Squadron of the 75th Cavalry Regiment of the US Army, a "small unit from the midwest", and studying the "huge impact" of war on soldiers (some no more than 20 years old). His plan was also to photograph civilian bomb victims and the work of an Italian charity, Emergency. He was into his fourth week but not making much progress. It is his pattern to get frustrated and send friends despairing emails ("I'm a rubbish photographer… I don't know why I am here"). But he knows himself well enough by now to recognise this as a staging post: his pictures come gradually: Trust, he says, is key. Often, a project comes into focus only as it is ending.

They were in Sangsar, in rural Afghanistan, nicknamed "Heart of Darkness" by the Americans because it is where Mullah Omar, one of the founders of the Taliban, had his mosque. "Imagine the most basic of combat outposts with sandbags, mud, ramparts, no proper electricity, no running water. To go out on patrol, you went through a wire. You could be under fire within a hundred metres of the base." And they had been fired at, only the day before, from a small, abandoned compound.

On 7 February, the plan was to search that compound. What was it they were searching for? "It's a question that sums up the war. I don't think anyone knew – chasing shadows." Although, he adds, they were checking on a sniper to see where he had been shooting from.

The compound was a mud hut with a small wall around it. The patrol consisted of six Americans and six Afghani National Army soldiers. The Afghans were supposed to be taking charge but a disagreement had broken out about who was to do the searching. "The Afghans were refusing, saying the compound would be full of booby traps." For about 15 minutes, the soldiers had been standing about and walking across a "little bit of flat ground". It felt, therefore, like a safe spot. While the sergeants were chatting, Duley turned to talk to an American soldier. And, at once, he felt "a click in my right leg" – the pressure plate that set off the landmine. "It is pretty instantaneous from click to explosion. And yet everything seemed to go into slow motion. I was tossed by the blast but there was not much noise – just bright, white, hot light. I remember seeing myself from outside my body. Not a religious experience but intense heat and fire and the strangely calm sense of flying through the air."

He did not pass out: "You go to a place that is beyond pain. It is funny how it is almost more painful to fall over and scrape your knee than to be blown up. Your body goes into incredible protection mode." What he saw, after "landing with a thud" was beyond his comprehension. His left arm was ripped to shreds. "There were white bones where the fingers should have been, the skin was peeled back off the hand and smouldering. It was like a horror film. I was terrified I might be paralysed because I tried to sit up but could not move." He did a "stocktake" of his body. "I could see clearly, I had my right hand. I could think. And what I thought was, I can still work as a photographer." (The first thing he would later say to his sister was: "I am still a photographer" – he "needed that goal".)

A different sort of stocktaking ensued, as each soldier shouted his name to ascertain who had been hit. "And I was letting them know it was me." But nobody could come to Duley until they had checked for secondary devices. Minutes seemed to last an eternity: "You just want somebody there." When Sergeant Chris Metz, leading the patrol, reached him: "He was fantastic. He asked questions about American football and whether I had a girlfriend. He kept me grounded. I felt very light-headed. My initial thought was that I was going to bleed to death quite quickly."

People are said to review their lives in flashback when they think they are about to die. For Duley, it was a flash-forward. He remembers: "I thought about Jen and how I knew she was the person I had been looking for all my life. I remember thinking I wasn't ready to give up on that. I thought about kids and how much I wanted them and about work. I knew how much I wanted to carry on work. And I kept shouting at the top of my voice, 'I am not fucking dying in Afghanistan.'"

The tourniquets were the first things that really hurt. He remembers asking: "Am I dying?" And there was a moment of reckoning: "The stretcher wasn't fully unrolled, it was ending way too soon. I could see bits of clothing and flesh in the tree above me." He saw a soldier's face turn grey at the sight of him – that frightened him. The sergeant offered him a cigarette and, although he had given up years before, he took it. "There was a strange Marlboro man moment when they propped me up against this canvas thing and the guy fed me a cigarette. It was calming and enjoyable – normality in the total abnormality of the situation."

Duley remembers being lifted into the Black Hawk medevac helicopter and the pain of it. He describes the down draught from rotor blades blowing dust into his face and the heat and people all around. But his will to survive was absolute: "I remember thinking: that's the first stage done… I've made it to the helicopter."

He is still in touch with medics, Cole Reece and Mo Williams, who flew with him on the 20-minute flight to the Nato military hospital at Kandahar airfield. They were used to heavy fighting – if Williams looked "befuddled" on the flight, he explained in a recent email, it was because he was astonished: every other triple amputee they had tried to get back to Kandahar had died. "And you were chatting away, asking pertinent questions…" At the time, he told Duley: "You are a fucking hell of a fighter."

What Williams did not know then was how much Duley had to fight for. And this is the bit that – if it were made up by a scriptwriter – you'd dismiss as an unfeasible subplot. He tells me about Jen. He had known her for a couple of years – the friend of a friend. She had been interested in photography. They had become familiar through letters – were pen-pals, e-friends. It was not until they met, face to face, not long before he went to Afghanistan, that he fell in love: "My heart leapt – I was absolutely sure she was the person for me." They went on several dates before Christmas. And he wrote from Afghanistan: "I told her I was in love with her and absolutely sure and wanted us to be a couple." But here is the twist: he never saw her reply. "She wrote a letter to say she felt the same way. It arrived the day I got blown up."

Duley was at the Nato hospital for two days before being flown to Birmingham, where his brother, David, and sister, Sarah, put everything – families and careers – on hold to be with him. He had, right at the start, given out Jen's phone number and his brother dutifully rang her but "no one in the family knew who she was". Duley was in intensive care and worsening: he got a lung infection, his kidneys packed up and, on 26 February, the doctors summoned the family to his bedside because they thought he was not going to pull through. For two months, it was touch and go. Visitors were kept to a minimum. Jen wrote every day and his sister read her letters aloud.

"Just to hear that she loved me and that it didn't matter what happened, that it made no difference to her. I mean, the whole thing was a shock because I didn't even know she felt that way at all." And he stops, his voice breaks and he needlessly apologises. He tells me how he would ask his sister to reread the letters. He couldn't talk (because of a tracheotomy) but would "tap" emphatically.

His sister got the message in every sense: "Do you want Jen to come?" she asked. And, in mid-March, Jen did. Duley was "terrified" of how she might react to the sight of him. But from that moment on, Jen's steadfastness has sustained him. His family, too, he says, have kept him going: "It has brought us closer." And he clearly has many friends, who have reacted with relief on discovering that he has retained his "dark sense of humour", that he is the person he always was.

Then he tells me a bizarre fact: his career as a photographer started in a hospital bed. He grew up in East Coker, Sussex, the youngest of five children, the son of an engineer (his father is now in his 80s and has been "wonderful"). He was keen on athletics and American football and, at 17, had gone to the US, hoping to attend college there. But he was involved in a car crash that smashed his knees and his plans. He spent six months back in England, in hospital. ("My surgeon said I would need operations on my knees later on. I have proved him wrong. My right knee is completely cured.") During this time, his godfather died and left him his camera (an Olympus OM10) and Unreasonable Behaviour, the autobiography of war photographer Don McCullin. Duley was bowled over. He ordered every teach-yourself-photography book he could and read them in hospital. As soon as he was home, he set up a darkroom in his bedroom: "I was obsessed from the moment I took my first photograph. I wanted to make photography my career."

At that point, many of his school friends were in bands. Duley played an "uncool" violin and bassoon; his camera gave him "credibility". In a sense, it was his instrument: "Everyone in a band has a big ego – they love having pictures taken." He felt he was in a band himself. He studied at Bristol and Bournemouth, but it was on the strength of his portfolio of photos of friends that he found his first jobs in London. It was the early 1990s, at the birth of Britpop – "a brilliant time". And his career went from strength to strength.

It was not long before he was getting commissions from GQ, Esquire and Vogue. He remembers a shoot with Mariah Carey where he realised "the image is bigger than the person and what I was photographing was the image". He took pictures of Christian Bale for Disney, was paid a small fortune but felt uneasy about the "corporate" portraits he had taken. He had moved into a world of high gloss and laboured at it. He was getting work as a fashion photographer, telling himself he must aim to be the new Mario Testino. But success and disillusionment were, all the time, growing together. In 2002, there was a turning point. He was taking pictures of a Big Brother star in a Soho hotel when a sordid argument broke out about whether she had agreed to do a topless shot. "I remember thinking, how have I ended up here? This has nothing to do with my love of photography."

He completely lost his temper and threw his camera down on the hotel bed and – to his dismay – watched it bounce off the bed and out through the window into Charlotte Street. It was not just the end of his camera. It was, for a year, the end of his career. He moved to Hastings and became severely depressed: "I hardly left my house. I felt I had let myself down." Yet it was during this fallow year that he started to think about what he could do in the world. He had always been "moved by the news and by people's stories". And he began to think how photography could be a way to "record events for posterity".

It was the beginning of the idea behind the quarterly photographic journal he still plans to launch. Document will "tell unheard stories of those caught in conflict and economic hardship around the world and record their lives as a way to better our understanding".

Duley was not under any illusions. He knew this was no commercial initiative. He would have to fund himself. What he did was "quite radical". He put everything into storage and got a job as a carer, looking after someone with multiple sclerosis. He would work 24-hour shifts, seven days a week for six to eight weeks, continuously. He could not go out of the flat, so would see nobody else for that period. It was hard – he doesn't pretend it wasn't –but then he could go on photographic trips for four weeks.

In 2009, something extraordinary happened. He was photographing Bangladeshi refugees who had no access to medical support. Dying people were lining up in front of him, as if expecting him to cure them. In consternation, he took the village elder aside: "These people have to understand I am not a doctor. I can't help them." The village elder replied that they knew he was a photographer: "But it is important to them that people see what is happening to us."

It was a moment of validation and public recognition followed. In 2010, Duley was nominated for an Amnesty International media award: "Most of the photographers had ITN or BBC or Al-Jazeera after their names. I was the only person with just my name. I had done it from my bedroom, funded everything, commissioned myself."

I have kept the difficult question until last: why go back to Afghanistan? "Because the story I was working on is unfinished business. Because going back may be a way of making sense of what happened. And because it is nice to think that, just maybe, some kid who had had his legs blown off might look at me, see me back at work and be inspired."

His hope is that his plight may also put an end to his moral ambivalence – his guilt – at photographing, for whatever reason, other people's suffering. "Now I am going to feel much more comfortable," he smiles. "I'll be able to say, well, look what happened to me… we can have a laugh about it."

Duley is also a realist, however. He admits he is "terrified". He insists he is a coward. I can think of no better definition of courage than returning to Afghanistan in spite of being afraid. But in the end, he explains, it is all about independence: "I want my life back. I want to be where I was a year ago. I am desperate to take photographs again." Sometimes, he catches himself in a full-length mirror and can be reduced to tears. He has phantom pains from missing limbs and he worries about being "defined by my injuries".

He is not going to let any of this stop him. He has already achieved many "small victories" at the Defence Medical Rehabilitation Centre at Headley Court in Surrey. He can sit up (weeks of physiotherapy, because you don't have the counterbalance of feet and legs); he can roll himself into a wheelchair unaided (a formidable feat) and he has taken his first steps on prosthetic legs (Herculean strength required). What's more, he has always felt: "If you believe you can do something, you can make it happen." As I say goodbye, I tell him I know he will make it happen, that he is already working on it. On the way out, I glimpse Jen waiting to go up. "What an amazing man," I call out and catch her reply as she disappears into the lift: "Isn't he just?"