Nicole has apparently taken to wearing the waist-cinching undergarment Spanx.

“She sometimes wears two pairs at a time,” a pal of Nicole reveals to OK!. And while the new mom is keeping this secret from the public, her fiancé Joel Madden, 28, is all too familiar with them. “He’ll help her find them in her closet if they’re running late,” says the friend. “But he thinks she looks great just the way she is.”