Gwyneth Paltrow is in the best shape of her life -- but it didn't come easily.

"I never thought that I'd be considered to have a good body. I was bony up top and kind of dumpy on the bottom," Paltrow tells SELF's May issue. "But my trainer, Tracy Anderson, completely changed my legs, butt, arms and stomach. I feel better than ever, too."

But don't be fooled: even Paltrow has problem areas.

"When Tracy met me, she said that I had a long, square butt that she was going to redesign, and I was, like, 'Yeah? Good luck,'" Paltrow recalls. "The amazing thing is, she was right! And it's still changing!"

What's the secret to the Oscar winner's enviable bikini bod?

"I do 45 minutes of cardio five days a week, because I like to eat. I also try for 45 minutes of muscular structure work, which is toning, realigning and lengthening," Paltrow reveals. "If I'm prepping for something or I've been eating a lot of pie, I do two hours a day, six days a week for two weeks."

That's not all. "I do Tracy's dance aerobics classes. It took me a long time to learn the choreography when I started. I was so uncoordinated!  After 11 minutes, I'd pass out and cry and say, 'I can't do this anymore!'" Paltrow, 38, says. "Now I can't live without it. You do it to loud music, and it's fun."

The My Father's Daughter author -- who curbs cravings by snacking on raw almonds with raisins -- has made exercise a priority for each member of her family, too.

"Being active is part of our life. Moses is 5 now and Apple's turning 7, and they dance around with me. Apple is really into ballet and flamenco dancing now," Paltrow -- who married Coldplay's Chris Martin in 2003 -- tells the mag. "Taking care of yourself is being there for your kids, like how on a plane, they tell you to put on your oxygen mask first."