Jessica Simpson was ''extremely shocked'' to learn she was pregnant again.

The 'Fashion Star' mentor and her fiance Eric Johnson are expecting their second child later this summer and admit they didn't anticipate having a sibling for their 10-month-old daughter Maxwell Drew so soon.

She said: ''We were definitely extremely shocked.

''I don't know, apparently protection was just thrown out the window!''

Jessica - who famously gained over 50lbs when expecting Maxwell - says her second pregnancy has been the ''complete opposite'' of her first so far.

She explained to TV talk show host Ellen Degeneres: ''Maxwell was our focus, and then I was puking and lying on the couch.

''Like with Maxwell, I felt amazing. Like, I could do everything, eat everything. Do whatever I wanted. I had a lot of energy. This time around ... I'm like, exhausted, eating Tums. That's my snack of choice!''

And the 32-year-old beauty has vowed not to gain as much weight during this pregnancy.

She added: ''This time around I think because I was doing Weight Watchers and I felt super healthy, I'm not really craving as much and I know how hard it is [to take the weight off] so I'm trying to make healthier, wiser decisions.''

However, she insists Eric didn't care about the extra pounds she piled on.

She said: ''Apparently Eric still wanted me so ... I can gain as much weight and I will have a husband-to-be that loves me!''