Jessica Simpson is just rolling with it. The pregnant-again 32-year-old singer, designer and reality star revealed her expanding baby bump and curves in a tight leopard-print dress during an appearance on The Tonight Show with Jay Leno on Tuesday Jan. 15 -- and was typically frank with Leno about dealing with a totally unexpected second pregnancy just six months after the birth of daughter Maxwell Drew Johnson.

One plan that keeps changing? Simpson's intended wedding to her babies' dad, Eric Johnson. "We've had two different wedding dates, but he keeps knocking me up," Simpson joked of the former NFL pro, 33, to whom she has been engaged for over two years.

"We're doing it very backwards, I know... I'll just keep my legs crossed, I guess, this time," cracked the Fashion Star mentor. "Apparently it was a part of God's plan for my life," she continued. When she discovered she was expecting again, "I was extremely shocked," Simpson said. "Because I was going through a lot of hormonal changes, trying to get back to the old, vibrant Jessica. You know, it was kind of like a one-night stand. And it happened, all over again!"

This time around, however, the Weight Watchers spokeswoman is determined to have a decidedly healthier pregnancy. While pregnant with Maxwell, Simpson admitted she gained "a lot more than doctors would recommend."

"I was really happy to be pregnant and I didn't ever step on the scale," admitted the blonde, who eventually lost 50 pounds post-baby via Weight Watchers and a personal trainer. "I didn't realize you could gain that much weight that quickly."

Watch Simpson's glowing appearance on The Tonight Show now.

This article originally appeared on Usmagazine.com: Jessica Simpson Talks Second Pregnancy: Eric Johnson "Keeps Knocking Me Up"