Demi Moore is revealing more details about her split from ex-husband Ashton Kutcher in her memoir Inside Out

Demi Moore is revealing more details about her fraught relationship with ex-husband Ashton Kutcher.

The actress, 56, digs deep into her previous marriage to the actor, 41, with whom she was married for eight years before they divorced in 2013.

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PEOPLE is out to Kutcher for comment.

In her new memoir Inside Out, Moore writes she “went into contortions to try to fit the mold of the woman he wanted his wife to be.”

“I put him first,” Moore says in the book. “So when he expressed his fantasy of bringing a third person into our bed, I didn’t say no. I wanted to show him how great and fun I could be.”

Moore and Kutcher began dating in 2003 after meeting at a dinner with mutual friends and were married in 2005 before splitting in 2011 and finalizing their divorce in 2013.

She says the two had threesomes that left her with feelings of “shame.”

Image zoom Demi Moore; Ashton Kutcher Dimitrios Kambouris/Getty; David Livingston/Getty

“They were good people, but it was still a mistake,” Moore writes of the people she says she and Kutcher had sexual relations with. “I was strangely flooded with shame, I couldn’t shake the feeling that this whole thing was somehow my fault.”

Their threesomes caused Kutcher to stray from their relationship, Moore claims.

“Because we had brought in a third party into our relationship, Ashton said, that blurred the lines and, to some extent, justified what he’s done,” Moore writes of her former husband’s alleged cheating.

While Moore was filming her 2011 movie Another Happy Day, she claims Kutcher had cheated on her a second time with a 21-year-old woman.

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“I knew she wasn’t lying,” Moore says of the woman who claimed she’d slept with Kutcher. “He admitted it right away.”

The actress writes Kutcher moved out of their home shortly after.

On Monday, Moore told Good Morning America‘s Diane Sawyer she “lost me” after her split from Kutcher.

“I think the thing if I were to look back, I would say I blinded myself and I lost myself,” she said.

Coping through the pain, the star broke her 20-year sobriety and began abusing substances like Vicodin and alcohol. Her three daughters — Rumer Willis, 31, Scout Willis, 28, and Tallulah Willis, 25 — stopped speaking to her. And her former husband and friend, Bruce Willis, pulled away as well.

Isolated and in anguish, she weighed just 102 lbs. Then in 2012, the star was rushed to the hospital after smoking synthetic marijuana and inhaling nitrous oxide at a party.

“I guess the fundamental question that came forward for me was, ‘How did I get here?'” Moore told GMA, reflecting back on it all. “From where I started to what I’ve experienced, where I’ve been, how did I get here?”