TLC's Tionne 'T-Boz' Watkins on living with sickle cell disease

— -- Singer Tionne "T-Boz" Watkins is opening up about her battle with an incurable disease and how it affected her singing career as a member of the pop group TLC.

Watkins' new memoir, "A Sick Life: TLC 'n Me: Stories from On and Off the Stage," describes how she has been able to overcome the difficulties of living with sickle cell disease.

"The title means so much for me," Watkins told Robin Roberts in an exclusive interview on "GMA." "It's a strong word, 'a sick life,' 'cause I've had it all. I was told I would never live past 30; I would be disabled my whole life and never have kids."

"But, no. Like I've traveled the world in TLC. I've worked with Michael Jackson," the singer continued.

Watkins, Lisa "Left Eye" Lopes and Rozanda "Chilli" Thomas were at the top of the music charts in the 90s, and the trio is the second-highest selling girl group in the U.S., according to the Recording Industry Association of America (RIAA.)

The combination of hip-hop, R&B and pop made the band's sound unique, but it was their powerful lyrics that resonated deeply with their audience.

"We talk about things that everybody can relate to. But we just do it in a fun way that you can dance to. And it's not like we're preaching, but it's like you get the message that we're in this together," Watkins said.

Their hit song "Waterfalls" paid tribute to the AIDS epidemic, while other hits like "No Scrubs" had a much more straight forward message.

When asked to define "a scrub," Watkins simply recited the famous lyrics: "A guy who can't get no love from me, because he's sitting on the passenger side pretending to have things he doesn't have."

"It's like, 'Dude, it's not even your car,'" she said of the brutally honest lyric.

Performing and touring while dealing with sickle cell disease, which affects nearly 100,000 Americans according to the National Institute of Health, created one of the biggest challenges of Watkins' life.

"The easiest way to describe it is oxygen isn't getting to our vital organs," Watkins described of the condition. "So, if it's your legs, you can't walk. Your arms, you can't even hold a pencil and write ... I went through so much."

She said her rigorous schedule caused her to spend months in the hospital recovering.

And the uphill battle for Watkins got a bit steeper in 2002 when the TLC sisterhood was shaken with the tragic death of Lopes, who died in a car accident in Honduras.

"That was one of the hardest times in my life," the singer said. "Lisa died like three, four days after I got out of the hospital. So, I was frail and 90 pounds. Which made me sick again. I'm like, 'What's goin' on?' Like, soon as something was good, it's just all, everything was just ... it was bad," Watkins said.

Following a 15-year hiatus, Watkins and Thomas are back together and celebrating Lopes' life in their lyrics.

"We keep her spirit alive throughout us and our music. And you feel her presence onstage. And nobody's gonna fill that void. She's up there rocking, and we're dancing with her," Watkins said.

The duo released their fifth and final studio album last June and Watkins has since recorded her first solo project.

"I just want to be remembered for the things that we really did in making a difference," Watkins said of the group's lasting legacy. "The fun and good stuff, the lyrical content, making a difference, and making people feel better."