TLC's Tionne 'T-Boz' Watkins on Her Debilitating Battle with Sickle-Cell Disease: I Was Told I Wouldn't Live Past 30

Tionne “T-Boz” Watkins is opening up about her debilitating battle with sickle-cell disease.

In her new memoir A Sick Life — TLC ‘n Me: Stories from On and Off the Stage — excerpted exclusively in the new issue of PEOPLE — the R&B star reveals how the blood disorder has impacted her life an how her kids are helping her through.

“I have to worry about it every day of my life,” Watkins, 47, says of sickle-cell disease. “You can be in so much pain you get delirious.”

Watkins was 7 years old when she was diagnosed with sickle-cell disease, which causes red blood cells to stick to vessel walls, blocking blood flow and preventing oxygen from reaching tissues; the lack of oxygen can damage organs and cause pain so severe it requires hospitalization.

When she received the diagnosis, Watkins says she was told she wouldn’t live past 30, that she couldn’t have children and that she’d be disabled her entire life.

“I looked around. Who was he talking about? I was going to be a famous performer,” Watkins writes in the book, recalling her visit to the doctor. “He was clearly mistaken.”

Indeed, Watkins went on to launch one of the most successful musical acts of all time, forming TLC with Lisa “Left Eye” Lopes and Rozonda “Chilli” Thomas in 1991. She continued to struggle with her sickle-cell disease, landing in the hospital multiple times a year due to the illness. (In 1996, she found out what she actually has is sickle-beta thalassemia with arthritis, a form of the disease that is often less severe.)

In 2000, Watkins proved her doctor wrong twice over: Not only did she live past 30 years old, but she also welcomed daughter Chase with then-husband Dedrick “Mack 10” Rolison. But her sickle-cell disease led to to harrowing post-birth complications.

• For more on Tionne “T-Boz” Watkins, pick up the new issue of PEOPLE, on newsstands everywhere Friday.

“On the first night, the nurses told me I needed to breastfeed her. It seemed like the right thing to do. And they make you feel so guilty if you don’t pop your t—–s out for the baby immediately,” Watkins writes in A Sick Life. “But sickle-cell patients need every drop of fluid they can get, and losing that much breast milk almost stopped my heart. Eventually, my body shut down and I fell into a coma. I spent three days unconscious in the ICU.”

Over the years, Watkins faced a series of tragedies: the 2002 car crash that killed her friend and bandmate Lopes, divorce from Rolison in 2004, and a brain tumor in 2006 which she battled successfully. The singer says her disease flares up when she gets emotional.

“Often, it’s hard to breathe or walk,” she writes of her illness in her memoir. “Some days I wake up consumed by pain. It’s like knives stabbing me over and over again in my joints. Chase gave me a reason to keep pushing through.”

And in May 2016, Watkins received something else to live for: a son, Chance, whom she adopted from her hometown of Des Moines, Iowa. And the singer says her expanded family keeps her strong.

“You don’t want your kids to know you think you might die. I don’t want my daughter or son to feel my pain,” she says. “I’ve got to keep a normal face on.”

Watkins, in her memoir, adds: “My life, my sick life has been tinged with illness. But I refuse to be defined by it.”

A Sick Life, written with Emily Zemler, is out now.