Tyra Banks landed a coveted Victoria's Secret contract and the Sports Illustrated Swimsuit cover before she was 24 years old
Sports Illustrated Swimsuit 2018 Launch Event
Credit: Craig Barritt/Getty

She made headlines for being the first black woman to grace the cover of Sports Illustrated’s Swimsuit Edition and later for fighting back against body-shamers on national television. Needless to say, Tyra Banks is used to having people talk about her figure.

But in a new memoir, Perfect Is Boring, written with her mother Carolyn London, the supermodel opens up about the challenges of being a body positive role model.

“I used to feel like my body was not mine,” Banks, 44, tells PEOPLE exclusively in this week’s issue, on stands Friday. “I’ve been too thin or too big. And I used to feel like I was betraying people if I lost weight.”

Initially rejected by high fashion brands for being too curvy, a determined Banks landed a coveted Victoria’s Secret contract and the Sports Illustrated Swimsuit cover before she was 24 years old.

RELATED VIDEO: Tyra Banks on Her First SI Cover: ‘Everybody Thought I Had Fake Boobs … They Just Stood Up Like That!’

Then in 2007, after paparazzi photos of Banks on vacation emerged, critics attacked her apparent weight gain. Furious, Banks fought back, appearing on her talk show and exclaiming, “Kiss my fat a–!”

Now, “I’m happy that the fashion industry is finally catching up,” says Banks. “What I’m hoping for is that the Ashley Graham‘s, the Gigi Hadid‘s, everyone is just models. Not plus, not short, not trans, not curvy. I just want it to be normal.”

More recently, Banks says her body changed since welcoming 2-year-old son York via surrogate.

“When he was first born, maybe because it was through surrogacy, I wanted to be bigger for him,” she says. “I felt that was love in a way. I wanted him to feel that cush and that nurture.”

But around nine months ago, when Banks visited the doctor for an ankle injury, she was told that losing weight would help her injury heal.

“I lost 30 lbs.,” says Banks, who now weighs 159 lbs. “And she was right. Now I’m a different body type. But I don’t feel like I’m betraying people. I’ve still got a–, I’ve still got boobs!”

  • For more on Tyra, pick up this week’s issue of PEOPLE, on stands Friday

Most importantly, “I feel physically good,” says Banks, who has a nutritionist. “And having a son later in life, I want to still be able to hold him and run around and chase him and not get spasms!”

Still, “I’m all about moderation, but you have to indulge,” says Banks. “My mom and I together are very dangerous. We love ice cream!”

Perfect Is Boring hits shelves April 3.