It's not just Kim Kardashian getting frustrating feedback from the scale these days.

Jessica Simpson "feels really, really frustrated" with her post-pregnancy weight loss, an insider close to the blonde beauty tells this week's edition of OK! magazine.

The Fashion Star stunner's effort to shed the pounds "has been really difficult this time around," the source said, adding that the mother-of-two "would just rather play with her kids than work out.

"She feels really guilty whenever she leaves them."

The star has help in her ace trainer, Harley Pasternak, who's preaching patience and persistence in her battle of