12/10/2013 AT 07:00 PM EST
has been very open about the issues that landed her in rehab
three years ago, but now reveals shocking details about the extent of her addiction.
The X Factor
judge was still a teenager when her problems spiraled out of control, and she reveals in an interview with Access Hollywood
that she went to desperate measures to make sure she had drugs with her at all times – even when she was flying around the world on tour.
"I couldn't go 30 minutes to an hour without cocaine and I would bring it on airplanes," the 21-year-old revealed.
"I would smuggle it basically, and just wait until everyone in first class would go to sleep, and I would do it right there," she said. "I'd sneak to the bathroom and I'd do it. That's how difficult it got, and that was even with somebody [with me]. I had a sober companion, somebody who was watching me 24/7, living with me. I was able to hide it from them as well."
Lovato admits that she became a master manipulator, lying "so that everything looked OK on the outside." And while her mother, Dianna, suspected that she was using drugs, when her daughter said she wasn't, she believed her. "I think for a long time I was in denial," Dianna admitted.
Lovato hit rock bottom at the age of 19.
"I was going to the airport and I had a Sprite bottle just filled with vodka and it was just nine in the morning and I was throwing up in the car," she said. "I had a moment where I was like, 'Oh, my God … that is alcoholic behavior.' [It's] no longer, 'I'm young and rebellious and having fun.' It was, 'Wow, I'm one of those people … I gotta get my s--- together.'"
The former Disney star also talked about her eating disorder, which began when she was 8.
"I started overeating, compulsively overeating," Lovato admitted. "I would bake cookies and then eat the whole pan … It was just this crazy battle going on inside me. It got really difficult. I would throw up and it would just be blood and it was something that I realized if I don't stop this, I am going to die."