The singer - who voluntarily checked into rehab in January after suffering from bulimia - said it was the continued pressure of thinking she needed to look a certain way, which caused the illness.
Opening up in a self-penned essay for Elle UK, the 27-year-old said her first day in rehab was the "scariest of my life" but knew she needed help when she felt her body "shutting down".
The star wrote: "I worried about what people would think. I was here for an eating disorder - but I knew people would assume I was here for other things."
In fact, her mum took to Twitter around the time to defend her daughter, saying she wasn't being treated for alcohol addiction but bulimia.
Patricia Rose 'Pebe' Sebert took to Twitter, writing: "She is in an eating disorder center. It IS NOT ALCOHOL OR DRUG RELATED!!!!!!!!"
Pebe then told Celebuzz: “She was dieting and she became bulimic. I remember over a period of a few months she got really skinny."
Kesha went on to say she wants to encourage her fans to love themselves, but said she had started not to herself.
"I've always tried to be a crusader for loving yourself, but I'd been finding it harder and harder to do personally," she said. "I felt like part of my job was to be as skinny as possible, and to make that happen, I had been abusing my body. I just wasn't giving it the energy it needed to keep me healthy and strong."
Kesha blamed the music industry, and constantly being in the spotlight, for her illness, saying it was added pressure.
"The music industry has set unrealistic expectations for what a body is supposed to look like, and I started becoming overly critical of my own body because of that," the 27-year-old singer wrote. "I felt like people were always lurking, trying to take pictures of me with the intention of putting them up online or printing them in magazines and making me look terrible.
"I became scared to go in public, or even use the internet. I may have been paranoid, but I also saw and heard enough hateful things to fuel that paranoia."
The star - whose hit Timber reached number 1 around the time she entered rehab - said she felt like she was lying to her fans.
"I felt like a liar, telling people to love themselves as they are, while I was being hateful to myself and really hurting my body," she said. "I wanted to control things that weren't in my power, but I was controlling the wrong things. I convinced myself that being sick, being skinny was part of my job. It felt safer somehow."
And she went on to insist she is "responsible", despite writing songs about partying, and said nights out aren't to blame for the illness.
She wrote: "Sure, I've written songs about partying, but my dirty little secret is that I'm actually incredibly responsible. I take my music and career very seriously, and certainly didn't land in this situation from partying. But I was cut off from the outside world and I imagined people making up stories at a time when what I really needed was support."
But the blonde bombshell is determined to stay well, having received the help she needed, and wrote: "During that time I began to feel a shift in my mentality and really started to understand my own self-worth. I started to not worry as much about what other people thought of me."
She added: "I'm not fully fixed - I am a person in progress - but I want to be part of the solution, not part of the problem. Even I need to be reminded that we are who we are."
The star ended by saying: "And when I say that, I f***ing mean it, now more than ever."