Sadie Robertson has been open about her struggles with body issues and an eating disorder, and in a new interview, the reality TV star says her Christian faith got her through some very dark times.

The Duck Dynasty star appeared on Dancing With the Stars in 2014. She was just 17 at the time, and she tells Entertainment Tonight's Unfiltered that she had "the body of a lifetime" during her time on the show because of all the rigorous physical activity the program demands. But once the show was over, the then-17-year-old star says "negative influences" in her life began undercutting her confidence by making comments about her appearance.

"They were such innocent comments at first, like, everything was great. But whenever my body started looking a little different, that's when the struggle came in," Robertson shares. "There were people in my life, who were just really negative influences, that would say things that were not uplifting about the way that I looked and how I needed to maintain the body that I had. It was so wrong. I was insecure at the time, so I believed them and thought, 'Oh, I need to push it.'"

She was also modeling at the time, and observations that she would look more like "a real model" if she lost 10 pounds had a further negative effect on her already tenuous sense of self-worth, she confesses.

"You can't stop thinking about your body, how you look, how you should eat," Robertson says of her subsequent eating disorder. "You're counting the calories, you're sizing up your legs and all those different things. You're just kind of completely gripped by it and that's kind of where I was. I would look at myself in the mirror and I would think, 'I'm fat,' and I was not at all."

Roberston adds that the turning point for her came when, "I started praising God and thanking him for the way that I looked," instead of finding fault with her appearance and her body.

"Instead I would tell myself, 'I am so thankful that I have this. I'm so thankful that my legs actually serve the purpose that they should and that they're able to run, that my arms are able to carry things. That my stomach one day, hopefully, will be able to carry a baby.' Just what we're actually designed and created for."

She also relied on faith to get her through the other self-doubts that plagued her after she shot to fame and felt like she could not measure up to peoples' expectations. That inspired her to create her Live Original ministry.

"The Lord said something so sweet to my heart. I just felt like God was saying, 'I'm not calling you to be this perfect person. I'm actually just calling you to be a sister and a friend to those who don’t have a sister and a friend,'" she tells ET. "I can be confident because I was created on purpose for a purpose."