"Oh, it hurt me," the 26-year-old singer-actress says in an interview in the March issue of Elle magazine, on newsstands Feb. 13. "Two or three weeks later? Yeah, I'd say it kind of hurt me."
Simpson and Lachey, 33, starred in the MTV reality show, "Newlyweds: Nick & Jessica." She filed for divorce in December 2005, after three years of marriage.
She made that decision, she says, after watching the 2004 romance "The Notebook" on a plane ride home to Texas. "I just figured out the statement," she says of the movie, starring Ryan Gosling and Rachel McAdams as star-crossed lovers. "It was about that moment of desperation. I needed to breathe."
Does she still keep in touch with the singer, who is dating MTV's Vanessa Minnillo?
"Mm-hmmm," she tells the magazine. "He's so much a part of my life, how could I not be? Any guy that's going to be with me from this day forward has to understand that. You want to help me find a guy?"
(It appears that's not necessary. Simpson has been photographed recently with singer-songwriter John Mayer, and in her profile in Elle, the writer noted that he spotted e-mails from Mayer on her computer.)
She says she "is so happy right now," but declined to discuss her love life. "I want to tell you everything, but I have to sew my lips together," she says.
Asked whether she's in love, a grinning Simpson plays coy: "I didn't say yes."