In an interview with Health magazine, the now 27-year-old "All About You" singer revealed she weighed under 100 pounds back then, and was obsessed with watching what she ate.
"When I was 17, I weighed, like, 98 pounds," she told Health in the mag's December issue. "I was totally obsessed with everything I put in my mouth. I was way too skinny. Not cute. And my body wasn't that healthy-my hands would cramp up a lot because I wasn't getting the nutrition I needed. That constant pressure of wanting something different than I had? I regret that. I feel like there was way too much time spent thinking about that."
The singer felt that pressure again after she give birth to her son Luca, saying that she felt like everyone was "so hard" on her because it took her a year and a half to drop her baby weight.
In spite of all of that, she kept working at it, and got back in shape by boxing, running hills in her neighborhood and doing two a days with her trainer. Now that her body is back, Hilary is learning to embrace it, even though she sometimes still struggles with her body image.
"This is the body that I have. I have a very athletic build, and I am so proud of what my body has done for me. I had the best, healthiest, strongest pregnancy," she continued. "And I feel good about myself. But I feel like I'm always in a 5-pound battle, because being 5 feet 2, everything is going to show on me!"
Adding that her biggest health regret is "constantly worrying that my body is not good enough," Hilary makes sure to maintain her workouts to keep her attitude in check.
"I work my butt off in the gym-and, yes, it's because I want to be fit, but it also puts me in a positive mind-set. If I don't have that for a week, I start to get more agitated and impatient; I get in a funk."