"Oh, it hurt me," Simpson tells Elle in its March issue. "Two or three weeks later? Yeah, I'd say it kind of hurt me."
(After their November 2005 separation, her ex was photographed with Laguna Beach star Kristin Cavallari. He's now dating MTV's Vanessa Minnillo.)
But Simpson, 26, says she's still in touch with Lachey, 33. "He's so much a part of my life, how could I not be? Any guy who's going to be with me from this day forward has to understand that."
She won't say whether that guy could be John Mayer, 29, with whom she's been linked off and on since the summer.
"I want to tell you everything, but I have to sew my lips together," she says. "It's hurt me in the past." (Still, a glimpse of her e-mail inbox reveals a block of about 10 e-mails from Mayer, including one with the subject line, "Texas girl.")
When the interviewer comments, "I feel that with this new privacy of yours, I'm going to wake up one morning, pick up the paper and read ..." Simpson interjects: "That I'm married! Maybe."
Asked if she's "totally in love right now," Simpson grins and says, "I didn't say yes."
If she's taking pains to keep her love life low-profile, it's because of the tabloid firestorm set off by her split from Lachey after they'd revealed the inner workings of their marriage on Newlyweds: Nick & Jessica.
Courtesy of Elle Magazine
She will say, though, that she thought there was hope for her marriage up until a few days before she and Lachey announced their split. So what changed? "I watched The Notebook on a plane home to Waco to be with my grandparents," she says. "It's a great love story."
The movie itself, she says, was "not what sealed it. I just figured out the statement. It was about that moment of desperation. I needed to breathe."