Mariah Carey just opened up about her battle with bipolar disorder, in an exclusive interview with PEOPLE.

The songstress, who was diagnosed in 2001 after her public breakdown, said she didn’t want to believe she had the disorder at first.

“Until recently I lived in denial and isolation and in constant fear someone would expose me,” she told the magazine. “It was too heavy a burden to carry and I simply couldn’t do that anymore. I sought and received treatment, I put positive people around me and I got back to doing what I love — writing songs and making music.”

The Grammy Award winner said that she decided to seek treatment after years of ups and downs in her career and her romantic life, which she says were “the hardest couple of years I’ve been through.”

Carey, who has sold over 200 million records and has 18 number 1 singles, reveals she is on medication to treat her bipolar II disorder.

“I’m actually taking medication that seems to be pretty good. It’s not making me feel too tired or sluggish or anything like that. Finding the proper balance is what is most important,” Carey said.

The mother of two, who’s working on a new album, said she had trouble sleeping for years and had thought she suffered from insomnia.

“But it wasn’t normal insomnia and I wasn’t lying awake counting sheep. I was working and working and working … I was irritable and in constant fear of letting people down. It turns out that I was experiencing a form of mania. Eventually, I would just hit a wall. I guess my depressive episodes were characterized by having very low energy. I would feel so lonely and sad — even guilty that I wasn’t doing what I needed to be doing for my career.”

She said that she is in a place in her life where she can open up about her mental health struggles.

“I’m hopeful we can get to a place where the stigma is lifted from people going through anything alone. It can be incredibly isolating,” she said. “It does not have to define you and I refuse to allow it to define me or control me.”