'20/20': Demi Lovato opens up about bipolar diagnosis, wants to 'open up the eyes of young girls'

demi-lovato-strong-tattoo.jpg Demi Lovato was a teen pop star with a seemingly perfect life. But her gorgeous looks and soaring voice were hiding a lot of darkness - cutting herself, bulimia and bipolar disorder. She opens up to Robin Roberts on "20/20" about her struggles, including how it affected her family.

"My mom was terrified of walking into my room in the mornings because she didn't know what she would find. Because it had become that serious," says Lovato.

As it got worse and worse, she ended up physically striking one of her backup dancers.

"I was performing concerts on an empty stomach. I was losing my voice from purging. I literally was so emotionally whacked out that I took it out on someone that meant a lot to me," she says.

It was at that time Demi Lovato checked into Timberline Knolls, a treatment center for women struggling with addictions.

"I had no idea that I was even bipolar until I went into treatment. I was actually manic a lot of the times that I would take on workloads, and I would say, yes, I can do this, I can do this, I can do this. I was conquering the world, but then I would come crashing down, and I would be more depressed than ever," says Lovato, of her bipolar diagnosis and mood swings.

But what kept her going were thoughts of her family and now she wants to be a role model for young girls - someone who can hit rock bottom and climb out a stronger person.

"A picture of my little sister, on my little bulletin board, was one of the main things that kept me going. I just kept thinking, 'OK, set this example for your little sister," Lovato says. "The real reason why I'm sitting down with you is to open up the eyes of so many young girls, that it doesn't have to be this way."

It's also why she has gotten the "strong" tattoo on her wrist (pictured above) - over the place where her scars were.

You can watch interview clips here.

Photo/Video credit: ABC