Jessica Simpson was "extremely shocked" to learn she was pregnant with her second child just months after welcoming her first baby.

The blonde star is currently pregnant with her second child after giving birth to daughter Maxwell in May.

In an interview on Ellen DeGeneres' talk show, Simpson admitted both she and fiancé Eric Johnson didn't anticipate adding to their brood so soon.

She quipped: ''We were definitely extremely shocked. 'I don't know, apparently protection was just thrown out the window!'

She added: "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!''

Simpson - who sported a big baby bump with daughter Maxwell - hopes to keep fit throughout her pregnancy.

The blonde beauty explained: ''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.'

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