Demi Lovato opens up about a dark period in her life and how she learned to live with herself.  (Photo by Ethan Miller/Getty Images)

Demi Lovato opens up about a dark period in her life and how she learned to live with herself. (Photo by Ethan Miller/Getty Images)

Demi Lovato once popped bills and snorted cocaine and had an uncontrolled wild streak that she reveals was fueled by early fame as a Disney teen queen and making lots of money.

“I was riding this wave of entitlement and superiority and they were in an impossible position because there’s no manual that explains how to deal with the sort of teenager I was,” she explains in a revealing new interview.

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It’s hard to believe at 21 that she’s already ridden the full cycle from child star to rehab and back. The most important thing she did, she said, was come clean with herself.

“When you are no longer hiding anything, you don’t worry about what is going to get out,” she tells London’s Daily Mail.

“I don’t care who knows about my life, and now that I am an open book a huge weight has been lifted off my shoulders.”

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She’s taken all of her past baggage and turned it into a soapbox to help deliver a message to kids who may be dealing with the same problems she faced.

She calls herself a “beacon of hope for the next generation.”

The New Mexico native got her start in show business as a child actor on the kid’s show “Barney & Friends.” Her break out role came in 2008 on the Disney Channel television movie “Camp Rock.”

As a result of the part, Disney signed her to their label Hollywood Records. She released an album,Don’t Forget, the same year It went gold, selling more than 500,000 copies, and she was on the fast track.

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Disney crafted a sitcom “Sonny with a Chance” just for her. She was not only working on the show, but continuing her music career. The pressures were enormous, and she was only 17.

“Everything skyrocketed, which was awesome, but the negative side was that I thought, ‘Right, I am working like an adult so I should be able to party like an adult,’” recalls Lovato.

“I was making a bunch of money and when my parents would get on to me for drinking and staying out, I would say, ‘I pay the bills, so what are you going to do?’”

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In Nov. 2010, everything came crashing down while Lovato was on tour with the Jonas Brothers in South America.

She got in trouble for breaking the tour curfew and got in a heated shouting match with a back-up dancer, whom she thought had told on her.

Lovato lost it and physically assaulted the dancer, Alex “Shorty” Welch, who was clueless about the incident.

Her career crashed, seemingly overnight. Demi left the tour and went straight to rehab to deal with a range of issues. “Sonny with a Chance” went on hiatus after only two seasons.

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By then, she was dealing with an addiction to pain pills and snorting cocaine. Her life was a living hell.

“I was performing concerts on an empty stomach. I was losing my voice from purging. I was self-medicating and I was so emotionally whacked out that I took it out on someone that meant a lot to me,” she said.

Things go so bad, her mother refused to let her see her little sister, Madison.

“Mom saying that made me realize that my life was a shambles and, although I had a lot of success, I was also very alone and miserable,” she says.

In rehab, she learned that she had a bi-polar disorder, one minute manic and the next severely depressed.

The diagnosis helped turn her around. After leaving rehab, she began publicly discussing her struggles and problems bulimia and cutting. She also attends AA meetings and hasn’t had a drink in two years.

“We are a different breed, we alcoholics, but it is just like having any other disease – you have to learn to live with it,” she says.

Lovato started by learning to live with herself. And that’s what she urges other people to do, too.