Taylor Swift shares a lot with her fans, but she kept quiet about a secret struggle with an eating disorder — until now.

In the 30-year-old singer’s new Netflix documentary Miss Americana, she gets candid about her body image and how internal and external criticism led her to “starve” herself and “just stop eating” earlier in her career, which left her weak onstage. Swift, who said the disorder is now behind her, also revealed that paparazzi photos served as a “trigger” — and tied it all the way back to when she was 18.

In the doc, which premiered at the Sundance Film Festival Thursday with Swift in attendance, the Grammy winner spoke candidly about her body and food issues after a scene showing paparazzi waiting outside her front door.

“It’s not good for me to see pictures of myself every day,” she said. She went on to explain that there were times in the past when she saw “a picture of me where I feel like I looked like my tummy was too big, or… someone said that I looked pregnant … and that’ll just trigger me to just starve a little bit — just stop eating.”

The Cats star, who stands at 5-foot-10, went on to say, “It’s only happened a few times” and admitted, “I’m not in any way proud of it.”

Swift said the disorder impacted her health the most when it was going on while she was performing, specifically during her 1989 world tour in 2015. However, she was healthier for her Reputation tour three years later.

“I thought that I was supposed to feel like I was going to pass out at the end of the show, or in the middle of it,” Swift said. “Now, I realize, no, if you eat food, have energy, get stronger, you can do all these shows and not feel [enervated].”

She went on to say she now accepts “the fact that I’m a size 6 instead of a size double-zero” and admitted she was defensive in the double-zero era when the topic of her weight came up.

“‘What are you talking about?’” she recalled saying to anyone questioning her eating. “Of course I eat… I exercise a lot.’ And I did exercise a lot. But I wasn’t eating.”

In Variety’s cover story, Swift spoke more about her secret struggle admitting that it was hard to let down her guard about it and include it in the doc. However, she trusted director Lana Wilson with the way it was depicted.

“I didn’t know if I was going to feel comfortable with talking about body image and talking about the stuff I’ve gone through in terms of how unhealthy that’s been for me — my relationship with food and all that over the years,” she said. “But the way that Lana tells the story, it really makes sense. I’m not as articulate as I should be about this topic because there are so many people who could talk about it in a better way. But all I know is my own experience. And my relationship with food was exactly the same psychology that I applied to everything else in my life: If I was given a pat on the head, I registered that as good. If I was given a punishment, I registered that as bad.”

And Swift recalled a specific tabloid headline when she was just a teen that stuck with her and seemingly started it all.

“I remember how, when I was 18, that was the first time I was on the cover of a magazine,” she said. “And the headline was like ‘Pregnant at 18?’ And it was because I had worn something that made my lower stomach look not flat. So I just registered that as a punishment. And then I’d walk into a photo shoot and be in the dressing room and somebody who worked at a magazine would say, ‘Oh, wow, this is so amazing that you can fit into the sample sizes. Usually we have to make alterations to the dresses, but we can take them right off the runway and put them on you!’ And I looked at that as a pat on the head. You register that enough times, and you just start to accommodate everything towards praise and punishment, including your own body.”

Swift said she “never really wanted to talk about” her eating disorder before and admitted, “I’m pretty uncomfortable talking about it now. But in the context of every other thing that I was doing or not doing in my life, I think it makes sense” to have it in the film — and now out there in the world.

Miss Americana arrives Jan. 31 on Netflix and in select theaters.