1230JesSimpson113011_01_X17.jpgJessica Simpson is taking a bit longer to lose the baby weight than originally planned!

Just a few weeks after giving birth to baby Maxwell on May 1, the new mom had her first Weight Watchers weigh-in, and she's gained about 70 pounds, according to US Weekly.

Jess has been hired as the new spokesperson for the weight-loss company, and her $4 million contract requires that she shed 20-30 lbs -- at least! -- by the end of August, or she misses out on the big payday. If that 's not enough motivation, we don't know what is!

"Jessica has always had issues with junk food," a Simpson pal told the mag, and she's enlisted her mom, Tina, and a few pals to do the program with her, "to help keep herself in check," the insider says.

Simpson, who celebrated her 32 birthday on July 10, has also been breast-feeding to help slim her down, and is given up those high-calorie margaritas she loves so much.

You can do it, Jess!