"I can't help but be a different person now that I've had kids," the singer and actress, 40, tells the May issue of Redbook, on newsstands April 20. "That really does change your whole perspective on life for the better. I definitely feel like I've grown up."
It took a little while to get up to speed. Lopez relied on husband Marc Anthony, who had two sons with previous wife Dayanara Torres, to teach her the basics of diaper changing. Lopez says she was almost afraid to touch the babies at first "because I might hurt them, because they were only five pounds each."
After two years as a mom, she is now a pro.
"My main priority now is that my kids are happy; that's my No. 1 focus in life," she says. "Are these little people happy, content, and getting everything they need? Everything after that is secondary. Before, my work was my main priority – even above myself."
The kids, in return, have nourished her. "I think the biggest thing they've taught me is what loving someone is and what it should feel like," she says. "This is what unconditional love means. It's crazy, but it's heaven and earth."
And when she can't be with them, she feels the downside of love: guilt. "I didn't know that feeling before," she says. "You don't know about it because nobody ever tells you. I think it's because women are a little ashamed to admit it. You feel guilty whenever you can't have your kids right there with you on your hip."
Lopez has a busy spring and summer planned. Her first film in three years, The Back-Up Plan, comes out this month, following by a guest-starring role on Glee and the summer release of her new CD, Love?.