The 26-year-old even said she had considered plastic surgery when she was younger because of how nasty people were.
After the show and her 35-point dance, Willis spoke to ABC News on why she decided to open up about her past.
"I feel like I've gotten to a point in the past year and it's why I wanted to share it," she said of not being nervous to share such intimate details about her life. "I think it's a really important message. Social media is such a breeding ground, unfortunately, for negativity and I wish if I can have any impact of making that more of a place of positivity and support for people than that would be my biggest wish."
She also wanted people to feel like they are "not alone."
Even Willis' dancing partner Valentin Chmerkovskiy, who admits having a hard time crying, said he got emotional and almost teared up watching her story.
He posted a message after the show on Instagram that read, "proud to be partnered with such an incredible woman. fearless spirit, genuine humility, and an enthusiasm for life that inspires everyone around her."