Jessica Simpson Says She Erased John Mayer's Number After He Called Her 'Sexual Napalm': 'It Was Shocking'

'He thought that was what I wanted to be called.'

Jessica Simpson is detailing the final days of one of her most high-profile relationships.

In her upcoming memoirOpen Book, the 39-year-old singer recounts her relationship with John Mayer, whom she dated on-and-off following her 2005 divorce from Nick Lachey. Their contact ended in 2010 after Mayer told Playboy that Simpson was "sexual napalm."

"He thought that was what I wanted to be called," Simpson tells People, who published excerpts of her book. "I was floored and embarrassed that my grandmother was actually gonna read that."

"A woman and how they are in bed is not something that is ever talked about," she adds. "It was shocking." 

Simpson tells the outlet that the comment "made it easy" for her to "walk away" from the relationship.

"He was the most loyal person on the planet and when I read that he wasn’t, that was it for me," she explains. "I erased his number."

Simpson notes that Mayer has "publicly apologized" for the comments -- he told The New York Times that he was "far out of touch" in a 2017 interview -- and adds that she's grown up since then too.

"I know that he’s publicly apologized and I don’t want to take that away from him," she says. "I think he knows a lot of this about me already but he doesn’t know the perspective I have as a woman. That was Jess in her 20s."

"He loved me in the way that he could and I loved that love for a very long time. Too long," she adds. "And I went back and forth with it for a long time. But it did control me."

Their relationship was intense from the beginning, when they met at a 2005 GRAMMY party in 2005. At the party, Mayer complimented her songwriting abilities and began penning notes to her.

"He’d walk into a room and pick up his guitar and you’d swoon," she recalls. "I didn’t really know the man behind the guitar. And that was my mission."

In her book, Simpson adds that "again and again, he told me he was obsessed with me, sexually and emotionally."

Simpson, however, found herself insecure in his presence and was, she writes, "constantly worried that I wasn’t smart enough for him."

"He was so clever and treated conversation like a friendly competition that he had to win," she writes. "My anxiety would spike and I would pour another drink. It was the start of me relying on alcohol to mask my nerves."

ET has reached out to Mayer for comment.

In 2014, four years after ending things with Mayer for good, Simpson met her now-husband, Eric Johnson, with whom she shares three children.

"I never had that kind of connection before," she says of Johnson. "He’s a very selfless and loving person."

Open Book is due out Feb. 4.