With the upcoming publication of her powerful memoir, Open Book, excerpted in this week's PEOPLE, Jessica Simpson reveals for the first time that she was sexually abused as a young girl

Jessica Simpson Reveals in Brave New Memoir: 'I Was Killing Myself with All the Drinking and Pills'

Five years ago Jessica Simpson had an offer to write a motivational book “to living your best life.” But in her heart, she knew she couldn’t go through with it.

“I didn’t feel comfortable talking about myself in a way that wasn’t honest,” says Simpson, 39. “I’m a horrible liar.”

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With the upcoming publication of her powerful memoir, Open Book, excerpted in this week’s PEOPLE, Simpson reveals for the first time that she was sexually abused as a young girl. The resulting emotional pain, along with other stressors, including career pressures, led her to self-medicate with alcohol and stimulants — a dependency that would later prompt her doctor to tell her her life was in danger.

“I was killing myself with all the drinking and pills,” she writes.

The star got sober in November 2017 and hasn’t had a drink since. “Giving up the alcohol was easy,” she says. “I was mad at that bottle. At how it allowed me to stay complacent and numb.”

Image zoom Jessica Simpson Mike Rosenthal

Therapy, she says, was the hard part. As she writes, “With work, I allowed myself to feel the traumas I’d been through.”

The abuse began when she was 6 years old, “when I shared a bed with the daughter of a family friend,” she writes. “It would start with tickling my back and then go into things that were extremely uncomfortable.”

Frozen in fear, she worried it was somehow her fault. “I wanted to tell my parents,” she writes. “I was the victim but somehow I felt in the wrong.”

When she was 12 years old, she told her parents, Tina and Joe Simpson, while they were on a car trip.

Her mother slapped her father’s arm and yelled at him: “I told you something was happening.”

“Dad kept his eye on the road and said nothing,” Simpson writes. “We never stayed at my parents’ friends house again but we also didn’t talk about what I had said.”

Image zoom Jessica Simpson on the cover of PEOPLE Mike Rosenthal

In the years that followed, as she skyrocketed to fame with her big voice and the reality tv show Newlyweds, which documented her three-year marriage to Nick Lachey, her fans fell in love with the young woman who spoke from the heart.

But she buried her anxiety and the pain and trauma she had experienced. Only her closest friends and family knew the truth.

In 2010, the singer who runs a billion dollar clothing line the Jessica Simpson Collection, found her soul mate in Eric Johnson. They married in 2014 and now have three kids, daughter Maxwell, 7, son Ace, 6, and baby girl Birdie, 10 months.

In one of the book’s most moving scenes, she writes about hitting rock bottom after a Halloween party at their home in late 2017. That’s when she told her closest friends: “I need to stop. Something’s got to stop. And if it’s the alcohol that’s doing this, and making things worse, then I quit.”

Her friends gathered around her in a group hug and haven’t left her side since. With the support of her parents and help from a team of doctors and twice weekly therapy, she’s been sober since that day and calls her newfound clarity “a continual gift.”

“When I finally said I needed help, it was like I was that little girl that found her calling again in life,” she says. “I found direction and that was to walk straight ahead with no fear.”

“Honesty is hard but it’s the most rewarding thing we have,” she says. “And getting to the other side of fear is beautiful.”

Image zoom Jessica Simpson’s Open Book

Along with the audio book she narrated, Simpson is also releasing six new songs which tell her story.

She hopes the book (and music) will help others to know they are not alone.

“It’s been a long hard deep emotional journey,” she says, “one that I’ve come through the other side with pure happiness and fulfillment and acceptance of myself. I’ve used my pain and turned it into something that can be beautiful and hopefully inspiring to people.”

For more from Jessica Simpson and an exclusive excerpt from Open Book, pick up the latest issue of PEOPLE, on newsstands Friday.