Revealing interview ... Jessica Simpson and Jay Leno on The Tonight Show.
Jessica Simpson says she has delayed her wedding twice because fiance Eric Johnson keeps "knocking [her] up".
The star is currently expecting her second child with Johnson, and the couple also have eight-month-old daughter Maxwell. Simpson appeared on US TV series The Tonight Show on Tuesday, where she joked about postponing her nuptials again.
"We've had two different wedding dates, but he keeps knocking me up," she said, laughing.
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"We're doing it very backwards, I know ... I'll just keep my legs crossed, I guess, this time."
Host Jay Leno then asked Simpson if she had planned to get pregnant so soon after the arrival of her first child. The star replied "Nope!" with a smile, before admitting it was a big surprise.
"Apparently it was a part of God's plan for my life," she said.
"I was extremely shocked ... 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!"
The singer and actress has vowed to be "more sensible" with her eating regime while pregnant with her second child, and said she won't eat "everything in sight".
"I was really happy to be pregnant and I didn't ever step on the scale," she said.
"I didn't realise you could gain that much weight that quickly. [I probably gained] a lot more than doctors would recommend. I didn't really make any healthy good decisions."
Simpson went on to discuss her recently announced NBC sitcom.
The show will be "loosely based" on her life, with Leno cheekily asking her if it would focus on a girl who keeps getting pregnant.
"Yes, and how that girl deals with that and everything else," she said.
"I will be playing myself, which is pretty easy. We don't have a name yet, we're just now in the process of casting everyone, doing the pilot. I will be playing myself but we'll have actors playing Eric and my dad. That'll be funny."