Jessica Simpson reportedly "feels so fat."

The singer-turned-designer gave birth to 9lbs. 13oz. daughter Maxwell Drew on May 1. During her pregnancy Jessica gained around 60lbs.

The star is a spokesperson for Weight Watchers and is following the company's program as she attempts to drop her pregnancy weight.

Jessica is said to be struggling to return to her normal size.

"She'd love to be out and about with little Maxwell, showing her off, but, unfortunately, she feels like crawling under a rock, she feels so fat," a source told the American edition of OK! magazine.

Jessica's low self-esteem is adversely affecting her relationship with fiance Eric Johnson.

"She's convinced herself that he's losing interest because she's not hot anymore," the source continued. "Of course that isn't trueEric thinks she looks beautiful no matter what, and he's always telling her that."

Eric believes they should postpone their wedding until Jessica is in better spirits.

"But at the same time, he's adamant that they should totally hold off and set the wedding date when Jessica's feeling good about herself," the insider explained. "Jessica is fighting him on it, but Eric's not backing down. In the end, it's really for her own good."