'Pretty Little Liars' star Troian Bellisario returns to painful past in new film

— -- "Pretty Little Liars" star Troian Bellisario is returning to a painful time in her past with her upcoming film, "Feed," which she wrote and stars in opposite "Harry Potter" actor Tom Felton.

The film, which debuts next month, is based on her struggles with an eating disorder. In a new interview, Bellisario, 31, opened up to "Liars" director Lesli Linka Glatter about the new film and that difficult period in her life.

"I found there were so many people who thought that it was about losing weight or being skinny, and I couldn't quite get them to understand that it was about control on a very, very literal level," she explained in the latest issue of Interview.

"I couldn't get anyone -- even the people who loved me the most, even my boyfriend or my mother or my father -- to understand what that experience was truly like for me."

That is why she began writing the screenplay that would become "Feed." She actually finished the script before she was even cast in the role of Spencer on Freeform's "Pretty Little Liars."

Now that the series is in its final season, she's been able to focus on bringing the story to the screen. Even so, reliving that part of her past wasn't easy.

"It was like engaging with an addiction," she said. "One of the things I really wanted the film to explore was that once you have this relationship, once you have this mental illness or this disease, it never really goes away."

In the film, Bellisario and Felton play privileged twins Olivia and Matthew Grey, who are split apart when an unexpected tragedy hits. "Feed" will be released digitally and on demand starting July 18.

"Pretty Little Liars" will wrap on June 27 after seven seasons.

Bellisario told "Good Morning America" last month, "I'm just glad for all this secret keeping to be done because it's been stressful for us."