Nick Carter: 'I Don't Know How I Am Still Alive'

Nick Carter is enjoying the success today of the reunion tour of the 1990s boy band that made him famous - the Backstreet Boys - but the singer said it almost wasn't so.

"In some ways, I don't know how I am still alive," Carter, 33, told ABC News' Abbie Boudreau in a Sept. 17 interview at the DP House in Hollywood.

"I was self-medicating intensely," he said of his struggle to battle depression in the years after the band made it big. "You're talking about, you know, hydrocodine, vicodins, you know, all these derivatives of opiates."

'90s Pop Stars: Where Are They Now?

Carter is putting it all out there, and more, in his new memoir, "Facing the Music and Living to Talk About It," that covers everything from his drug and alcohol abuse to his relationship with a notoriously public socialite.

"I was just a boy toy. Don't get me wrong," Carter said of his high-profile romance with Paris Hilton. "And, honestly, I was under the influence a lot during that relationship."

Melissa Joan Hart Reveals Hookup With Nick Carter

Carter was arrested in 2005 for driving under the influence and his abuse of drugs and alcohol was so severe that it caused changes to his brain, he said.

The source of his addictions came from the emotional and mental abuse he said he suffered as a child as part of a show business family that went on to star in their own reality show on E!

The show, "The House of Carters," debuted in 2006 and followed Carter and his family members, including his younger brother, Aaron Carter, also a pop star, and their sister, Leslie Carter, who later died from an apparent prescription drug overdose.

"It was a train wreck show," Carter told Boudreau. "That's what it was. There was no thought behind it. Just put a bunch of people in a house that have issues and let 'em explode."

Carter said he finally turned his life around after he was diagnosed with a heart condition caused, at least in part, by his hard-partying lifestyle.

"It's a swelling of your heart muscle due to the buildup of toxins in your heart," Carter said.

Now drug-free, Carter is also newly engaged - to fitness expert and actress Lauren Kitt - and ready to take on the world and not become a Hollywood statistic.

"I feel like I've become such a better person that I'm not afraid to show the world now who I've evolved to become," he said. "I don't want to be one of those people that they say, 'Oh, well, remember that guy Nick Carter - you know, from the Backstreet Boys? You know, he's just another one of those child stars that ended up a tragedy.'"