Jenna Talackova sat down with Barbara Walters for an exclusive interview. Photo: Heidi Gutman/ABC

Jenna Talackova, the transgender woman who was temporarily disqualified from a Canadian beauty pageant, said that even as a child she knew she was "in the wrong body." While still a teen, she pursued her desire to become more feminine - through hormone therapy and more feminine clothing - and, as a result, endured name-calling like "tranny" and "it."

"People would just, walk, lurking around my locker, like, 'I can't believe it, oh my God,' " she remembered.

Talackova sat down with ABC News' Barbara Walters for an exclusive interview. She said she was just four years old when she realized she was different.

"As soon as I was conscious, I just always knew that I was not what they were saying. It wasn't right," she said. "I thought that I was in the wrong body."

Talackova went from local beauty queen to a headline-grabbing transgender rights activist in the span of just a few weeks after the Ms. Universe Canada pageant informed her that she would be disqualified from the competition because she was not a "naturally born female."

Representatives for Donald Trump, whose company owns Ms. Universe pageants, said earlier this week that he would reverse the decision to disqualify Talackova and that she would be allowed to compete in the pageant.

Shortly thereafter, Talackova's lawyer, Gloria Allred, criticized Trump for having the "natural born female" rule at all.

The Trump organization later released a statement saying that pageant rules had "been modernized to ensure this type of issue does not occur again."

Talackova, who was born with the name Walter Talackova, had gender reassignment surgery at the age of 19 but her physical transformation to a female began long before that.

By the eighth grade, she had grown her hair long and was wearing feminine pants. At the age of 14, she started hormone treatments, which helped her develop breasts and gave her skin a more feminine quality.

The treatments "made me feel better, mentally," she said.

After years of counseling, Talackova obtained letters from doctors testifying that she qualified for sex reassignment surgery - surgery that the Canadian health system paid for.

The procedure used the skin of Talackova's penis to create a vagina. She called the surgery "intense" but ultimately "rewarding."

"It was terribly painful, but seeing something on your body for that long and not being able to look at myself in the mirror because I couldn't stand seeing the other part, it was actually very rewarding, too," she said.

Talackova also had other surgeries - she was given breast implants and also had her Adam's apple removed.

From the Canadian government's standpoint, Jenna is officially a woman. She changed her Canadian driver's license, passport and even her birth certificate from male to female.

After her surgery, Talackova found love - a boyfriend who is about her age. He knows her history, she said.

"He's very supportive… just an amazing man," she said.

Talackova said she's now committed to helping others.

"I feel like the universe, the creator just put me in this position as an advocate," she said. "And now it's like this, and I'll take that position. If it's helping anybody else, my story and my actions, then I feel great about it."

Watch the full story on the latest episode of "20/20."