You might never know it from Jennifer Lopez's sexy and confident image and many successes on stage and screen, but the newly confirmed 'American Idol' judge was filled with insecurities earlier in her career.

"The biggest insecurity I had was my singing," J. Lo says in Cosmopolitan magazine's October 2013 cover story. "Even though I had sold 70 million records, there was this feeling like, I'm not good at this. And while I was married to Marc [Anthony], he helped me get over it. He kept telling me, 'You're the only one holding yourself back from reaching your full potential as a singer. You have to let go' ... I was always so insecure and just kind of going along. Then I grew, little by little, and realized, wait a minute, this is not a fluke. I'm not a mistake -- I work my ass off. And I know what I'm doing."

For the cover of the magazine's 'Sexy Power Issue,' La Lopez dons what can best be described as a sexy power outfit: belly-baring black satin and lace with a jacket slung over her shoulder. Her knowing, closed-mouth smile says she's in control and she's enjoying it. Her long, wild hair suggests that she had just been spending some quality time with boy-toy Casper Smart!

Her former back-up dancer boyfriend may be much younger, but he's managed to teach Jennifer a thing or two about relationships. "It's funny, early on with [Casper], I remember telling him how I have a real button on being ignored," she reveals. "And he was like, 'Listen, if somebody ignores you, then forget them. They don't deserve to have your attention.' But it's funny. Sometimes when we don't get it, we try to get it in a negative way, you know?"

The new issue of Cosmo hits newsstands on Sept. 10 -- check out another image from Jennifer's photo shoot below!

Jennifer's 'Sexy Power' style + stance in full effect