LeAnn Rimes Shape Magazine Oct. 2010 [Cover Picture]

Bustin’ up homes does a body good. Controversial ountry queen LeAnn Rimes shows off her bikini body on the October cover of Shape Magazine. But perhaps even intriguing, Rimes spills the beans on why she left her husband of more than six years — dancer Dean Sheremet — to shack up with the also-married Eddie Cibrian, who she met and bedded after the pair co-starred in the 2008 Lifetime Original Movie Northern Lights.

“My relationship with Dean was great, but ultimately it wasn’t a fulfilling marriage for either of us,” the singer, 28, explains. “We got married so young: I was 19 and he was 21, so as we got older, we grew apart.”

“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,” LeAnn adds.

The “I Need You” crooner calls her rigorous exercise regimen and devotion to fitness “a life saver” as she battled depression in the wake of an image-crushing and nearly career-ending infidelity scandal.

“Sometimes I felt so depressed I didn’t want to get out of bed, so just getting to the gym—even for a few minutes—was a big accomplishment,” she says. “It 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.’”

Rimes — who now lives with Cibrian, 37, and his two sons, Mason, 7, and Jake, 3, with estranged wife Brandi Glanville — bares her bikini bod like a badge of honor.

“I feel like my body is changing and that I’m growing up into a woman. 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. My butt—well, I’ve always had a butt—but now I definitely have a butt, which I love. I’ve taken up weight training three or four times a week, and I do a lot of squats. I’ve also been doing more cardio, even though I absolutely despise it. I try to get in a good 20 to 25 minutes before I do anything else; if I don’t do it first, it won’t happen.”