leanncovercheat.jpg LeAnn Rimes covers the October issue of Shape Magazine, and the country star finally explains why she cheated on husband of six years, Deane Sheremet and left him for current beau Eddie Cibrian.

LeAnn tells the mag, "My relationship with Dean was great, but ultimately it wasn't a fulfilling marriage for either of us. We got married so young: I was 19 and he was 21, so as we got older, we grew apart." LeAnn added, "I understand why people are disappointed in me, especially since I grew up as America's sweetheart. I think any relationship is hard to get out of, and I don't think the way I did it was right."

Though she's found love with Cibrian, whom she met on the set of Lifetime's film Northern Lights while she was still married to Sheremet, LeAnn says she was so depressed when the cheating scandal broke, she "didn't want to get out of bed." However, working out "really did make me feel better and kind of saved me. It gave me a bit of sanity. Even now, on days when I'm really frustrated, I'll walk into the gym and say to my trainer, 'We're boxing today. For an hour. I need to hit things.'"

It certainly shows! The singer always looks fabulous, and the red hot bikini she's sporting on the cover shows off her toned and taut physique. Of the sexy shot, LeAnn says, "I probably weigh about 6 pounds more than when I shot that cover, but my body fat is the lowest it's ever been. I've gained a lot of muscle, and I feel like I have more curves too." Hey, at least she's in love and in shape!