Jessica Simpson has confirmed her second pregnancy definitely wasn't planned.

"Oh no, nope. Apparently it was a part of God's plan for my life. I was extremely shocked," the Fashion Star mentor said during a Tuesday night appearance on The Tonight Show with Jay Leno.

"I was shocked because I was going through like a lot of hormonal changes, trying to get back to the old, vibrant Jessica. And you know, it was kind of like a one-night stand. And it happened, all over again!"

Simpson, who told host Jay Leno she's due in the summer, added that she suddenly felt like, "I'm pregnant again! Here I go again!... [Fiance Eric Johnson] was really proud of himself, actually."

Simpson made the announcement she's expecting Johnson's second child in a Christmas Day tweet in which she posted a holiday photo of Maxwell Drew -- her eight-month-old daughter who was born on May 1 -- sitting in the sand with "BIG SIS" written in the sand in front of her. A source told Us Weekly beforehand the pregnancy wasn't planned.

"We've had two different wedding dates, but he keeps knocking me up," Simpson joked with Leno.

"We're doing it very backwards, I know... I'll just keep my legs crossed, I guess, this time."

After Maxwell was welcomed into the world, the actress and fashion designer began a reported $4 million endorsement deal with Weight Watchers which resulted in her dropping more than 50 pounds before her weight-loss was unexpectedly derailed by the new pregnancy.

"I gained a lot -- a lot more than probably doctors would recommend. But I had fun... I didn't really make any healthy, good decisions. Once I had Maxwell, I realized it all wasn't just water weight and I really had to work hard. So in four months I lost over 50 pounds," Simpson explained.

"The last time, I ate everything in sight. I was really happy to be pregnant and I just didn't ever step on the scale. I was the person who turned around on the scale and said, 'Just don't tell me, I'm having fun!' And I guess I didn't just realize you could gain that much weight that quickly."

Simpson told Leno that the news of her second pregnancy definitely caught Weight Watchers offguard as well.

"I think that they were as shocked as I was. Because it was so soon after having Maxwell and I was hitting all these goals and everybody was celebrating. And then all of a sudden it was like 'Ahh, here she goes again!' But they were really supportive because what can you do?" the reality TV star said.

Simpson noted expecting her second baby has been different than her first experience because she's been getting sick a lot. After saying she hopes to start feeling better soon, she also told Leno she plans to utilize a healthier diet this time around.
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!

As for Simpson's career, NBC has picked up a pilot presentation for a television comedy starring the new mom.

"It's basically loosely based on my life," Simpson said.

Leno then jokingly suggested that meant the sitcom will be about a girl who keeps getting pregnant.

"Yes," laughed the Fashion Star mentor. "And how that girl deals with that and everything else. I will be playing myself, which is pretty easy... It's not titled yet. We don't have a name yet. We're just now in the process of casting everyone and all that."

Added Simpson, "I will be playing myself but we'll have actors play Eric and my dad. That'll be funny. There's a lot of things that happen in my life where I'm like, 'People have to know about them.'"