Demi Lovato's full interview with Robin Roberts aired on 20/20 last night, and the 18-year-old actress shared even more details about her personal struggles with the show.

In the interview, Lovato reveals that she did attack dancer Alex Welch, and added that the constant bullying about her weight was what led to an eating disorder. “I was compulsively overeating when I was eight years old. … So, I guess, for the past 10 years I’ve had a really unhealthy relationship with food," she says. Lovato also discussed her cutting, telling Roberts, ”It was a way of expressing my own shame, of myself, on my own body. I was matching the inside to the outside. And there were some times where my emotions were just so built up, I didn’t know what to do. The only way that I could get instant gratification was through an immediate release on myself.”

How low did the Disney starlet go before she realized she needed help? “I was performing concerts on an empty stomach," she continues. "I was losing my voice from purging. I was self-medicating. I was not taking medication for depression, and I literally was so emotionally whacked out that I took it out on someone that meant a lot to me.”

Demi seems to be in a much better place now, and though it was a difficult decision to go public with her personal life, she wants to make a difference. “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," she says.