Tyson Fury steps out of his back door on an ordinary morning in Morecambe, near Lancaster, with three black bags of rubbish in each huge hand. "Hello, mate, it's binmen day," he says quietly in greeting, before nodding towards two refuse collectors approaching his small corner bungalow with wide eyes and eager expressions. Emptying the dustbin of the unbeaten British and Commonwealth heavyweight champion is clearly a highlight of their day.

"Are you fighting again soon?" one of the awed men asks as he looks up at a giant who is 6ft 9in tall and weighs 18st. "Yeah," Fury says. "Next Saturday, in Manchester. And live on Channel 5. Should be good."

"Amazing," the binman murmurs.

I am more amazed that, having arrived at his home, Fury offers me such a limp handshake. There is no knuckle-crushing welcome from a 23-year-old boxer hyped as a Gypsy hard man intent on claiming glory for the travelling people he is said to represent. Instead, the big man leads me diffidently round the back. Halloween is over but a massive plastic pumpkin still blocks the front door of the house he shares with his 21-year-old wife, Paris, and two children, Venezuela and Prince.

The sight of a two-year-old girl jumping around happily, and a four-week-old baby boy sleeping in a pale blue pram, prompts a discussion of their exotic names. "One night, while I was sleeping," the fighter says, "I thought of Venezuela. My wife is called Paris. I'm Tyson and [gesturing to his son] he's called Prince John James. If the girl had a normal name it wouldn't fit in, would it? I wanted to call the boy Patrick but the wife didn't want it."

Paris gives me a knowing look. "Ask him what name he really wanted for our son …"

"Jesus," Fury interrupts.

"That got a quick no from me," Paris sighs.

"Jesus Fury," the fighter says wistfully. "I like that name. A lot of Mexicans are called Jesus."

Does Fury have a desire now to visit Venezuela, as the country gave him his daughter's name? "South America?" he ponders. "Nah. What could I get in South America that I couldn't get here?"

"A good tan," Paris suggests.

This knockabout fun, however, is framed by darkness. It is not just the darkness of Fury's past or even the fact that his father, a former pro heavyweight called "Gypsy" John Fury, is currently serving a prison sentence for an assault which cost another man his eye. Something more distressing is embedded in Fury.

Yet, before revealing himself with unsettling candour, Fury continues conventionally for a man whose own name stems from his father's fascination with Mike Tyson. "Boxing is a dying sport really," Fury says. "Years ago the world heavyweight champion could be said to have reached the highest pinnacle of sport. Even in this country boxers were heroes. Think of Henry Cooper and Frank Bruno. No footballer was bigger than Frank Bruno. I don't think it will get back to that – never in a million years. People look to celebrities now.

"In British boxing today, Joe Calzaghe's gone. Ricky Hatton's gone. David Haye's gone. But I'm hoping I can bring it round. When I beat Dereck Chisora [at Wembley Arena in July] 3.2 million watched it on Channel 5. I've got an outspoken personality which gets people thinking, and my style of fighting is aggressive. Everything's on the line all the time. In my fights there's drama. So that can help."

Fury's Commonwealth title defence next Saturday against the Bosnian-born Neven Pajkic, who is now Canada's heavyweight champion, is being promoted along traditional lines. "I went ringside with Pajkic," Fury remembers, "and said: 'Oi, you and me, let's have a fight.' He chucks this dirty ring towel at me and says: 'C'mon let's fight now.' Everyone's jumping in and holding us back. It was pantomime.

"But I went on national TV in Canada and said exactly what I thought of Pajkic. I'd watched his fight and thought it was rubbish. From there it went really personal. He started calling me and my family names. I know this is terrible and I shouldn't say it, but I'm in the mode to do serious damage. When I go in there I'm trying to put my fist through the back of his head. I'm trying to break his ribs and make them stick out the other side. I don't like this kid. This kid has said some terrible things."

Fury sounds ominously Tyson-esque here. Of course the reality is different. He may have relatively fast hands but the Englishman is not a destructive hitter like the heavyweight force who gave him his name. Fury is a decent operator who is still inexperienced after just 16 professional contests. But, having interviewed Mike Tyson in his bleakest years, I feel the same chills when Fury talks alarmingly.

"There is a name for what I have," he says, "where, one minute I'm happy, and the next minute I'm sad, like commit-suicide-sad. And for no reason – nothing's changed."

Sitting in his armchair, wearing a vest and shorts, Fury looks at me evenly. "One minute I'm over the moon and the next minute I feel like getting in my car and running it into a wall at a hundred miles an hour. I don't know what's wrong with me. I'm messed up."

Can he overcome these feelings? "No," Fury says calmly. "I just live with them. I think I need a psychiatrist because I do believe I am mentally disturbed in some way. Maybe it was the fact that when I was a kid we didn't have a family life. My mother and father were always shouting and screaming and hitting each other. My dad had different women and different kids down the road. My mum had 14 pregnancies – but only four of us survived. We had a little sister born for a few days and she died. There had to be a funeral. That would affect you."

What happened last year with his father? "He knew the guy," Fury says softly. "They just bumped into each other at a car auction in Manchester. The guy started it. There were three of them against my father. The feller bit my dad on the face but as he shoved him back he punched the feller in the eye. And he lost his eye. He had to have the eye taken out because it got infected. The judge found my dad guilty of wounding with intent."

Fury himself does not seem a violent man. "I've never been in trouble in my life. I've not got a criminal record. Never had a fight outside boxing. So I'm very different to my dad."

He certainly appears more vulnerable than his father. "I know I've got nothing to be upset about," Fury says. "I'm British and Commonwealth champion, I'm doing OK. I've got a few quid in the bank. I shouldn't be upset. But I don't feel I've done any good at all. I thought when the children were born it would be a top thing. And when I became English champion I thought there'd be a great feeling – but no. I thought it must be because it's not big enough. Let me win the British title. But after I took that off Chisora there was nothing. At the end of the day what have I done? I've beaten another man up in a fight. I dunno what I want out of life, me. What's the point of it all?"

We talk about his wife, and children, while they sit around us. Trying to sound like a sage old soul I suggest that beyond his immediate family, there are always touching or amusing or interesting or stimulating moments in life. He is still young and his bleak perspective might become more rounded. "No," he says. "I don't think it's ever going to change. I can just see it going crazy. One loss in the ring and it's all over. So it's very serious. I know it could be all over every time I step into the ring."

Even if he says his travelling heritage means little to him, there are still experiences, and people, he should savour. "Yeah," Fury says, "but every day you're on a downward slope."

"I hear this constantly," Paris says. "But there are good days. If you'd come on a good day, you'd have been all right."

Fury leans forward. "I just want to get across how I feel."

"Sometimes I listen," his wife says, "but depression runs in his family."

Fury nods. "My three brothers are the same as me. But with us everyone is a tough guy. They don't talk like you and me are talking. But we all cry instantly. Look at me: 6ft 9, and if someone said this to me in my family I would just cry. All of us would. But nothing's talked about in our family. We just push other aside, or give each other a punch."

Fury is no longer working with his uncle, Hughie, his usual trainer. "Hughie and I have trouble getting on. But every time I've gone away from Hughie I've not looked so good. So it's a big step to leave Hughie at such an important time."

How will Fury cope if he wakes up on Saturday in this depressed state of mind? "I won't," he says. "I love boxing. It's not a horrible thing to me. I can't wait for the moment I step into the ring. I feel calm then. It's like everything has been forgotten. It's just me and him and we're going to go at it old school. But after that it's back to the reality and feeling angry – just with life. I'm looking for something different that's just not out there. But when I get in the ring I don't have this feeling I've got now. Right now, I really feel like smashing this place up."

I laugh nervously as Fury looks around his home. "I don't feel like that in the ring because, if I do, it's all over. An upset fighter is a beaten fighter."

Hearing all these swirling contradictions I try hard to believe that Fury does indeed find some strange refuge in the ring. He has the potential to one day contest a version of the creaking old world heavyweight title and, with a terrestrial television following in this country and a chance to fight in America next year, Fury's damaged sense of self might ease one day. And, for a man who left school aged 10, he speaks lucidly and piercingly about his deepest emotions.

"I love talking," Fury says, almost smiling. "It's one of my favourite things in life."

Some of the most memorable fighters over the decades have been great talkers – but few of them, bar Mike Tyson himself, have articulated the darkness within them in such a matter-of-fact manner. "I'm glad I've got boxing," Fury says. "I feel better in the ring. That's when I feel some relief."

And how will Paris feel on Saturday night? "I don't get nervous until, literally, I hear his music and he starts walking out," she says. "My stomach turns upside down. That's when you think, 'He's going in that ring against someone who wants to hurt him.' Before that it's OK because he's happy and excited and telling me he's going to win. It all changes when I hear the music but I remember to trust him. I always think he's going to be all right in the end."