Although former American Idol sensation Carrie Underwood has become one of the country music's biggest stars, fame has its downside – especially when it comes to dating, she says. "You never really know why somebody wants to be around you, or if they do genuinely like you," Underwood, 25, tells Allure magazine in the September issue. "I wish everyone had a label on their forehead so you could automatically tell their intentions. Sometimes you just wish that no one wanted anything from you." The star, who earlier this year was inducted into Nashville's Grand Ole Opry, recalls a time soon after her success on Idol when a guy who'd ignored her in college – clearly enamored by her newfound success – called saying that "he wanted to explain." Fame hasn't helped create lasting relationships for her either. Earlier this year, Underwood split from Gossip Girl's Chace Crawford via text-messages. "We didn't have a fight. No one cheated," she clarifies. "It plain didn't work." As for Dallas Cowboys QB Tony Romo, who now is dating Jessica Simpson, Underwood says she still hears from him sometimes – but doesn't always pick up the phone. "We were both small town people doing very big things, and we relied on each other, dealing with fame," says the singer who claims the relationship wasn't serious. And now? "I don't know. The phone will ring and it'll be him, and I'll maybe not answer." Some of her reservations about opening up to people seem to stem from an old flame who cheated on her. "I don't want to name names, even though he probably deserves it, but he fooled around," she tells the magazine. "Oh, yeah, and lied! It was one of those things that everyone knew but me. He was a good liar. Nobody would come out and tell me. And he seemed perfect in every way." Added the singer: "I'm sure we've all run into these people, whether they're friends, boyfriends or girlfriends."