The `Fashion Star` mentor and fiance Eric Johnson are set to have their second baby together just seven months after Jessica gave birth to their daughter, Maxwell Drew Johnson, on May 1.
A source told Us Weekly magazine: "It definitely wasn`t planned. But yes, Jessica is pregnantagain."
Jessica, 32, has previously said of her daughter: "Motherhood is a dream, it really is absolutely amazing."
The former singer has been engaged to NFL player Eric, 33, for two years, and it was rumoured they had been planning to tie the knot in Italy next year.
Shortly after giving birth, Jessica was named the face of slimming brand Weight Watchers, and had been working hard with trainer Hayley Pasternak to lose some of the 60lbs she gained during her first pregnancy.
She said at the time: "I think anybody who`s gone through a pregnancy, after they have the baby, it`s like, `I need to do something about this.-
"For me, I really want to do something that is a lifestyle, because in the past, I`ve been known to yo-yo diet."