Lauren Conrad on the cover of Cosmopolitan (July 2009)

Reality star Lauren Conrad opens up about her former B.F.F. Heidi Pratt and her current B.F. Kyle Howard. Read why she's looking forward to leaving "The Hills" and living a life that is "a little more unplanned."

Lauren tells Cosmopolitan magazine that "The Hills" producers kept pushing her into situations with Heidi. "It's hard to look at somebody who used to be your best friend and say, 'We can't be friends. Too much has happened,'" she tells the magazine. "I'm trying to move on, but they won't let me. And when someone keeps pushing you into the same position, well…you get upset."

As for her life outside the show, Lauren seems to be the most comfortable when she's with her boyfriend Kyle: "I feel sexiest with him when I'm in sweatpants and no makeup."

It was recently reported that Lauren's former "Laguna Beach" costar Kristin Cavallari will be replacing her on "The Hills."

"I've always had another season to look forward to, but now life is a little more unplanned," she says of leaving the show. "It's really exciting."

For more of Lauren -- including info on her book and fashion line -- check out the latest issue of Cosmo magazine, on newsstands June 2.

I wasn't able to embed the vid, so you'll have to click on source to see it.