By Sally Garcia, EnStarz | Sep 22, 2012 02:46 PM EDT
Demi Lovato told Katie Couric that her weight issues date back to when she was 3 years old.
"The X Factor" judge, who has admitted to struggling with eating disorders and cutting, made the shocking revelation on "Katie" in an interview set to air Monday.
"I remember being 3 years old in a diaper and rubbing my hand over my stomach," Lovato, now 20, told Couric. "I remember thinking in my head 'I wonder if one day this will ever be flat?'"
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Lovato also opened up about her experience with bullying.
"I've always said I wished that they had just hit me in the face and gotten it over with," she said. "What they said to me sticks to me to this day and it [turned] me into the person I am today."
The singer also opened up about her experience in rehab. Lovato checked into a treatment center in November 2010 where she was diagnosed with bipolar disorder. She finished rehab in January.
"I remember walking around saying 'I'm in prison!."
"They needed to have those strict rules in order for me to understand how sick I was. I wasn't allowed to use the bathroom by myself," she added.
"We had specific phone times. There are tons of things you weren't allowed to have; you weren't allowed to have certain hair products or whatever that you could injure yourself with or possibly drink and you were just stripped of a lot of things."
Lovato is now judging "The X Factor's" second season alongside Britney Spears, Simon Cowell and L.A. Reid.
"The most fun about being on The X Factor is seeing people that really wow you and knowing that you saw them before they were going to become stars," she says.
Demi Lovato's Interview with Katie Couric will air on 'Katie' on September 24.
Watch an Excerpt of the Interview with Katie Couric Below:
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