Jessica Simpson revealed what went wrong in her marriage to Nick Lachey.

In her upcoming memoir, Open Book, the 39-year-old wrote candidly about her relationship to ex-husband Nick Lachey. The couple met at the Hollywood Christmas Parade in 1998 before dating and getting married on October 26, 2002. The couple then signed on to the MTV reality television show Newlyweds. The cameras almost constantly followed the couple around just months into their marriage.

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"He was my first love," she admitted to People, who obtained a preview of the upcoming book. "Nick loved the fact I was so strong in my faith and that I had this wide-eyed innocent approach to life. When he proposed in 2002, I said yes."

As they were growing up, the couple was growing apart while off-camera. "We were young and pioneering our way through reality television, always miced and always on," she wrote. "We worked and we were great at it but when it came time to being alone, we weren’t great at it anymore."

In 2005, Simpson filed for divorce after less than three years of marriage and seven years together. "We really got crushed by the media and by ourselves," she shared. "I couldn’t lie to our fans and I couldn’t give somebody hope that we were this perfect golden couple."

Although they are not together anymore and are each happily married, she has nothing but love and respect for her ex-husband. "I respect Nick very much," she wrote. "I was really young and my success hadn’t really begun. He knew me as this young innocent 18-year-old that had never been introduced to the world in so many ways. I went straight from my father to him. Nick’s very smart. He was eight years older than me, but he was also young."

Lacey is now married to Vanessa Minnillo and the couple shares three children together. Simpson is married to former NFL player Eric Johnson, the pair shares three children together.