Chaz Bono Chaz Bono

Chaz Bono says he has no doubt he was born a man.

"This is how I was born," he told ABC's Nightline about his gender reassignment surgery. "It's actually pretty simple if you look at. We all in the womb start out as female and then hormones come and we either stay female or we become male. I think of it as hormones that, you know, went in the brain but not in the body, and that's all being transgender is. It's just that the sex of your body and the gender of the brain don't match up."

Chaz Bono asks to change name, gender

Born as Chastity to Sonny Bono

and Cher, Bono, 42, changed his name to Chaz after undergoing the surgery two years ago. He began the process nearly four decades after first believing he may be a lesbian and more than a decade after coming out as one. "I just thought that something was wrong with me," Bono said. "Like I am not being a good lesbian ... because I was really a man so I never wanted to be a woman. That's how I was failing as a lesbian."Bono began the process in March 2009, receiving testosterone injections and having his breasts surgically removed. "If you are a man and you have breasts, any man would want to have them removed," Bono said. "It is scary for a woman to think about it because it is something that they are really attached to. Being male and having breasts is about the worst thing I could imagine."However, Bono remains a woman anatomically from the waist down, as that type of surgery is still risky. "That's not to say I wouldn't like a penis," he said. "I really would like one and I hope that someday I will get one."

VIDEO: Chaz Bono's gender journey

Bono documents his transformation on Becoming Chaz, which premieres Tuesday at 9/8c on OWN. He'll have a follow-up discussion on The Doc Club with Rosie O'Donnell immediately afterward at 10:30/9:30c on OWN.Although the long process took a huge toll on his family, including Cher and his partner, Jennifer Elia, Bono said things have since improved. His relationship with his mother continues to "move in the right direction," while his sex life with Elia is much improved thanks to the testosterone injections. "I risked a lot but I finally got to the place where I knew this is what I'm supposed to do," he said. "I had absolute faith in, no matter what, even if it was rocky or difficult, everything in the end was going to be fine, and it was. It has exceeded every expectation that I've had."Watch Bono's interview: