Former fashion photographer Giles Duley, 40, switched to photojournalism and, in 2010, was nominated for an Amnesty media award for his work covering acid burn survivors in Bangladesh. On 7 February this year, while on patrol with a US Army unit, he stood on a landmine, losing both legs and his left arm. He plans to return to photography as soon as he can. An exhibition of his work opens in London tomorrow.

When I put my foot down, I heard this click. Then bang. It was such a shock, like jumping into freezing cold water, when your mind suddenly can't process what's going on. This incredibly bright, white light and intense heat covered me. I was tossed into the air for what felt like ages. Then I crashed down, slap-bang on my side. There was no noise, no pain. Just deafening silence.

My left hand had flopped over my face. So when I looked up, it was through a hand ripped to shreds. The small white bones were completely exposed and all the flesh on one side of my arm was missing. Like something from a horror film, it was smouldering. I couldn't feel my legs, so I tried to sit up. My feet were no longer there. A nearby tree was covered in bits of my flesh.

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I knew I was badly hurt but I remember checking: do I still have my right hand? Yes. Could I still see? Yes. Could I think straight? Yes. I'm a photographer. If one of those three things had been missing I'd have been terrified. It meant I could still work.

In my twenties I'd been a music photographer enjoying the rock'n'roll lifestyle, snapping everyone from The Black Crowes and Marilyn Manson to Mariah Carey. I was interested in humanitarianism but wasn't sure how to get involved. One day, I just quit and put everything I owned into storage.

For three years I worked as a live-in carer for a vulnerable adult and would spend two months solidly caring and then go away to Sudan or another war zone for a month to take photographs. I wasn't being paid to take photographs, so I could take the ones I wanted to for their own sake. I contacted NGOs and charities to say: "What's going on that you think should be documented?"

I was in Afghanistan photographing civilian victims of war. I decided that I also wanted to photograph American troops. I was embedded with the First Squadron of the 75th Cavalry, 101st Airborne Division for about three weeks.

It was frontline stuff, a tiny desert outpost with surrounding sandbags. I knew how dangerous it was. Years earlier, I'd stepped on a landmine in Angola which hadn't exploded. Not many people survive two landmines.

On that particular day, I went out on a small patrol. I didn't need to go with the soldiers. That morning, I'd written in my journal that I was worried I wouldn't come back. I remember thinking: "I just won't go." As a photographer, I was there voluntarily. I could have said: "I'm not coming out with you today." But I didn't like to do that.

The area where I was standing had already been checked for mines. I turned around intending to go for a cigarette. I put my foot down and that's when I heard the click. Bang.

Everybody got down and lay in the dirt. One by one they called out their names to say they were fine. I kept calling, "Giles. Giles! It's Giles. I've been hit." Luckily, there was a senior medic on patrol that day. He put tourniquets on my arms and legs straight away and pulled them tight. That was the first thing that actually hurt. I kept saying: "Tell me, am I going to die?"

I willed myself not to pass out. Sergeant Metz was telling me about American football and kept me talking. He got me a cigarette and lit it. It was the best cigarette I've ever smoked.

I lied when one of the soldiers asked me about my girl. Jennie and I had been on a few dates before I went to Afghanistan. She wasn't my girlfriend, but I really wanted her to be. It sounds pathetic but I remember picturing Jen and thinking in my head that if she was mine I could keep going. Then I felt very guilty for telling them she was my girlfriend when she wasn't.

Suddenly, this helicopter came in as close as it could, sending dust and the heat of it everywhere. It was very painful being jerked up and down as they ran with me towards it. The helicopter guys came out wearing these big masks, which was very intimidating. They threw me into the back of the helicopter and we were off.

The helicopter medics couldn't believe I was conscious. I was the only triple amputee they'd seen that year who survived, let alone was talking to them and asking "incredibly pertinent questions" and apologising for the trouble.

From Kandahar I was moved to an intensive care unit in Birmingham. It was awful for Jen, because my family didn't know who she was. She and I had been friends for a couple of years. When I came back from Sudan for Christmas, just before I went to Afghanistan, we became very close. I had written to her telling her she was the girl of my dreams. But she didn't reply. That is, until the day of the accident, when she emailed to say she felt the same way. I didn't get it because it arrived after the explosion.

The first Jen heard of the accident was through my family that I was in intensive care. It was awful for her. She wrote me a letter for every day that I was unconscious. She wrote that it didn't matter what had happened to me and that she felt the same way I did. As soon as I regained consciousness, we started seeing each other. It's the weirdest start to a relationship I've ever had – being in intensive care together every day.

To step on a bomb, have your legs blown off and survive, is lucky. Everybody has a good-luck story. Mine was the fact that the senior medic was on patrol that day. Those who don't have a good-luck story are the ones who don't make it.

Giles Duley: Becoming the Story is on at KK Outlet, London N1 from 4 to 26 November. gilesduley.org