Jessica Simpson is revealing why her ex boyfriend, former NFL quarterback Tony Romo, broke up with her.

It all started when Jessica‘s ex, John Mayer, started to get back in touch with her. In “Open Book,” Jessica writes that she’d always tell Tony when John contacted her.

However, in 2009, she ran into John at her parents house, and Tony then found an email from him to her. The couple dated for two years before Tony broke things off in July of 2009.

“[Tony] accused me of seeing John behind his back. I hadn’t cheated on Tony at all, but I could not lie and say I hadn’t even seen him. ‘Nothing happened,’ I said,” Jessica wrote in her book. “Tony didn’t believe that for a second. And within that second, he broke up with me right there. Two years, gone with an email.”

“I could trust that Tony would never tell the press that John Mayer caused the breakup. It would imply that he wasn’t enough for me,” she added. “Tony soon realized I was telling the truth. Of course I didn’t cheat on him. But our breakup had been so ugly that it shocked me into realizing it had been necessary.”

Then, Jessica revealed, the drama with John wasn’t over.

“[John] had said all these things, practically asking my parents for my hand in marriage while I was in a serious relationship. Swearing to me up and down that he was a changed man,” she added. “Now here I was, ready to pledge my love back, and to kiss him as the curtain came down. And it fell on my head… All this time, all those years, he was breaking up with me to torture himself enough to get good material.”

“It felt inevitable to be in love with John, so I continued talking to him for months. But I knew now not to let him get close enough to shoot me down again,” she added.

Find out what else Jessica dished about John Mayer in her new book.