"I gained 70-ish pounds over two years," Pieterse recounted. "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 21-year-old actress said she had no idea why she suddenly started putting on weight, and had no idea how to deal with her problem until just recently, when she was diagnosed with Polycystic Ovary Syndrome, a hormone imbalance.
"Finally, I knew what this was happening to me," she shared.
Since starting the show, Pieterse said she's already lost 15 pounds and "most importantly, I'm feeling like me again."
"It's not an easy road, but being able to focus on getting myself healthy again and the fact that I'm seeing results now and getting better is all I can ask for," she added.
Hitting the dance floor for their prom-themed routine, Pieterse absolutely beamed as she and Savchenko pulled off a beautiful, strong and dynamic samba that earned some love and praise from the judges -- especially Carrie Ann Inaba.
"Most girls are sitting at home thinking, 'I wanna be like you,' that's what's happening right now." Inaba exclaimed. "The best part of being a judge on this show is watching someone like you really blossom into yourself. You are great out there."
Speaking with co-host Erin Andrews after the performance Pieterse opened up about her DWTS journey and her emotional road to getting healthy.
"I feel like I've always been a happy person and I've been so blessed with an amazing family and friends, but I went through a hard time," she shared. "So, feeling like me again means the world, honestly."
For their sweet, energetic performance, the beaming couple earned a score of 22 out of 30, putting them near the top of the night's scoreboard.
ET's Cameron Mathison caught up with Pieterse and Savchenko after Tuesday's show, where she opened up about how she hopes to spread awareness of her condition to other women who may unknowingly be suffering from it as well.
"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. "[A lot of it] could've been avoided, so if I can share that, that's really important to me."