Nothing breaks like a heart. Jessica Simpson has revealed she was “saddened beyond belief” when she heard ex-husband Nick Lachey had quickly moved on with television host Vanessa Minnillo.

In an extract from Simpson’s new memoir Open Book, the singer has hand-written a journal entry which talks about how Lachey started dating his now-wife Minnillo less than a year after they ended their four-year marriage.

“So, Nick, you’re with another already? Seems that you forgot the love you spoke to me,” Simpson writes in an excerpt obtained by Entertainment Tonight.

“I’m saddened beyond belief. Alone in the dark, with no one to call my own.”

It’s a universal feeling. No matter how a relationship ends, finding out an ex has moved on can feel unsettling, painful and at worst, devastating. And you’ve got to hand it to 40-year-old Simpson for being so honest.

Simpson and Lachey were married from 2002 – 2006. The no-holds-barred memoir also includes details about the final night they were together just prior to their divorce being finalised in 2006. Simpson says she was at home watching an MTV documentary about Lachey’s album What’s Left Of Me as well as an episode of “Making the Video” which documented the title track’s music video (a video that co-starred Minnillo).

“I just wanted to know what he thought of me now, because at that point I had no idea,” Simpson writes in her memoir. “I watched him portray himself as a victim, casting me as this selfish person. I knew he did this to hurt me.”

“So I called him,” she writes. “And I asked to meet him at my house … He rang the bell, and out of reflex I hugged him. I meant it, too. Despite my anger, I missed him.”

The exes then listened to all of his song’s about her on his new album.

“I was numb, just blank. How do you react when you find out you have apparently hurt someone so deeply that they feel entitled to such actions? I felt manipulated into some revenge fantasy, but I had put myself in this situation,” she says. “I didn’t know any other way to make it better, so I slept with him.”

Simpson said she felt no connection to Lachey that night.

“He didn’t stay the night. I was relieved because I could feel his hate. The whole situation was very dark,” she writes. “When he walked out the door, I knew I would never see him again.”

Lachey and Minnillo wed in 2011. They have three children Camden, 8, Brooklyn, 6, and Phoenix, 4.

Simpson married American footballer Eric Johnson in 2014. They have three children together, Maxwell, 8, Ace, 7, and Birdie, 2.

Open Book is available now.