04/23/2008 at 02:00 PM EDT
, who has been linked to such famous men as football star Tony Romo and Gossip Girl
's Chace Crawford
, says she's experienced heartbreak at the hands of an unfaithful boyfriend – but remains mum on the culprit.
"I've been cheated on a time or two. It's tough," she tells InStyle
in the May issue, on newsstands Friday. "I wouldn't recommend doing any property damage, though," she laughs, a reference to her Grammy-winning song "Before He Cheats" about a woman who trashes her boyfriend's truck.
"Now I'm to the point where you get one shot. Life's too short," adds the Season 4 American Idol
champ, who says that dessert is one way she heals from heartache.
"I'm a 'let it go, move on' kind of person. And ice cream is my friend. If anybody sees me eating a sundae and I look unhappy, something bad has happened," Underwood tells the magazine. "I am drowning my sorrows in fudge and caramel and whipped cream."
The singer also admits that she struggles with body image."I think about what I look like probably more than I should. But I think everybody is her own worst critic," she says. "Some days I step out of the shower, put my lotion on, and I'll be like 'Ugh, ew, ew.' "
She rarely goes out without makeup and keeps a food diary: "I'm OCD like that," Underwood admits. "I count calories, fat and fiber – which is important in making you feel fuller faster – and protein, especially when I'm working out."
Why is she so strict with herself? "If I put on five pounds, it's noticed immediately," says Underwood.
Still, she says, "I'm content with 90 percent of me. I like my teeth. Sometimes I wonder if my orthodontist realizes how important he was."
For more on the Carrie Underwood cover shoot, go to InStyle.com.