simpson091112_06_X17crop230flip.jpgJessica Simpson is already giving daughter Maxwell Drew Johnson a sibling! The Fashion Star mentor and her fiance Eric Johnson are expecting their second child, according to Us.

A source tells the mag, "It definitely wasn't planned. But yes, Jessica is pregnant again."

Maxwell was born only seven months ago at 9 pounds, 13 ounces. Jessica, who is still breastfeeding, recently lost 70-pounds in connection with her multi-million dollar Weight Watchers deal.

The source adds, "She really is overjoyed!"

Aside from news that they're going to be parents again, Jessica and Eric have yet to set a wedding date.