Ahead of its release, more excerpts from the book are being shared online. According to TMZ, Spears reveals that the former NSYNC member allegedly cheated on her with “another celebrity” while they were dating. The ex-couple’s romance began in 1999 before they split in 2002.

TMZ notes that Spears did not want to name her as she has a family and did not want to embarrass them. These shocking details come after Spears also revealed in her memoir that she had an abortion with Timberlake when they were teens.

“It was a surprise, but for me, it wasn’t a tragedy. I loved Justin so much. I always expected us to have a family together one day. This would just be much earlier than I’d anticipated,” Spears writes of the pregnancy in her new book. “But Justin definitely wasn’t happy about the pregnancy. He said we weren’t ready to have a baby in our lives, that we were way too young.” Spears went on to share that she decided to go through with terminating their baby because the former NSYNC member wanted her to. She writes,

“I’m sure people will hate me for this, but I agreed not to have the baby,” she writes in the book. “I don’t know if that was the right decision. If it had been left up to me alone, I never would have done it. And yet Justin was so sure that he didn’t want to be a father.”

In her new book, Spears also talks about another painful time when she used to be brutally criticized by the paparazzi and tabloids which led to her infamous 2007 head shave.

While speaking to PEOPLE, Spears shared how hard it was to look back on her past. “It’s hard to speak about,” Spears says of recounting her life’s darker moments, including “not getting a moment of peace, the judgments from strangers who don’t even know me, having my freedom stripped away from me by my family and the government [and] losing my passion for the things I love.”

“It is finally time for me to raise my voice and speak out, and my fans deserve to hear it directly from me,” she says. “No more conspiracy, no more lies — just me owning my past, present, and future,” she told the outlet.