Sasha Pieterse and her partner Gleb Savchenko may have sizzled on the ballroom floor with their prom-themed samba to Hailee Steinfeld's "Most Girls," but the road to get there was far from easy. During Tuesday night's Dancing with the Stars, the Pretty Little Liars star opened up about her personal struggle with weight.

"I gained 70-ish pounds over two years," Pieterse revealed on the show. "It was really, really hurtful the way people reacted. They were saying stuff like, 'She's pregnant.' 'You're fat.' They were angry, they were mad that I look like this. It was one of the hardest things I've ever been through."

The actress had no idea why she was gaining weight until recently when she was diagnosed with a hormone imbalance called Polycystic Ovary Syndrome. "Finally, I knew what this was happening to me," she added.

The 21-year old, who admitted she felt a personal connection to Steinfeld's song because of those struggles, triumphed on the dance floor and earned a respectable score of 22 out of 30. Now, she's using her platform to help others who may have the same condition.

Dancing with the Stars: Who Got the Sexiest Score on Latin Night?

"What I want [is] for people to have awareness because so many women have it and they don't know and if you don't catch it in time, it leads to [things like] ovarian cancer and breast cancer and all kinds of things that women deal with all the time," Pieterse explained to ET after her show-stopping performance. "[A lot of it] could've been avoided, so if I can share that, that's really important to me."

She'll next be seen reprising her role as Alison DiLaurentis in the Pretty Little Liars spin-off, Pretty Little Liars: The Perfectionists. In the meantime, catch her on Dancing with the Stars which airs Mondays at 8/7c on ABC.