Demi Lovato Flaunts Bikini Bod in New Twitter Pic

Demi Lovato used Twitter to post a photo of her new bikini body on Monday. The pop star wore a white halter-top two-piece and flashed a smile for the camera.

"I've been working so hard to get healthy and fit," she wrote. "I can't believe I'm about to do this but I'm so excited ... Here's my bikini time body!"

Since leaving rehab, Lovato has been open about her struggles with anorexia, bulimia and bipolar disorder. In an interview with '20/20,' the 18-year-old revealed that being "bullied for being fat" caused her body image issues.

"I never thought I'd ever feel confident enough to ever do that," she added. "I'm excited how far I've come since being completely ashamed of my body."

Recently, Lovato became a spokesperson for Seventeen and the Jed Foundation's  Love Is Louder Than the Pressure to Be Perfect campaign. She has already starred in an ad and PSA for the effort, and contributes to the magazine’s website.

"I want any girl/guy out there who struggles with body image or confidence to know that it IS possible to find peace with yourself," she continued. "It hasn't been easy, but it starts with a commitment to yourself ... Your mind ... And your soul. And trust me, I'm still working at it!! Haha."

Watch Demi Lovato Talk About the 'Love Is Louder' Campaign