Credit: Perry Hagopian/UsWeekly

Sweatin' her way back to a bangin' bod!

Former Bachelorette star Jen Schefft was overjoyed when she and hubby Joe Waterman welcomed their first child, daughter Mae, in November 2010.

Less joyous? Slimming down post-baby -- and finding a fitness routine that worked for her. When former PR exec Schefft, 35, got on the treadmill three months after giving birth, "I thought I was going to die!" she tells the new Us Weekly, out now. "I didn't realize how out of shape I was."

While carrying Mae, a nausea-plagued Schefft admits she "threw in the towel" with her diet -- indulging in Chipotle, pancakes and cheeseburgers daily.

How'd she finally find a way to get back her body -- dropping 40 pounds and fitting into a size 4 again? Bikram yoga, as suggested by husband Waterman -- and a diet defined by moderation rather than restriction.

Thanks to super-sweaty Bikram sessions, "I dropped 25 pounds right away. Those last 15 took a while," Schefft admits. "And I still have about 5 to go. I want my abs back!"

For more on Schefft's amazing slimdown, pick up the new Us Weekly, out now!