Jessica Simpson has revealed she's experienced many false alarms due to premature labor pains as an expecting mother.

"We have some time, [but] it doesn't feel like I have a lot of time. You have these things called Braxton Hicks, which are these contractions that scare the living daylight out of you! So in the middle of the night, I'm like, 'Eric! It's happening! It's happening!'" Simpson, who will serve as a celebrity mentor for the fashion designers on NBC's new Fashion Star reality competition, said of fiance Eric Johnson during a Monday night appearance on The Tonight Show with Jay Leno.

"But it's not supposed to happen yet. So, we kind of freak out a little bit, but then I read the blogs and it's like, 'This happens to everybody.'" 

Simpson said she believes the contractions have been a telling sign of how difficult giving birth will be when the time comes.

"I'm like 'Wow, labor is going to really hurt!' Like I have so much respect for my mom and all the women across the world. This is a tough thing here! And I'm wearing six-inch heels today. That's a lot of weight to carry on six inches," joked the reality TV star, who previously starred in VH1's The Price of Beauty and MTV's Newlyweds reality series.

While their baby girl's arrival is quickly approaching, Simpson explained the couple's wedding date may not be. 

"We're definitely going to be in each other's lives forever now. I want him to be my husband so bad, and I still want to wear the pretty gown and everything, so I'm going to have to wait until after the baby -- and now, she can just be in the wedding!" Simpson told Leno.

The reality TV star confirmed she was pregnant with Johnson's child in October, however reports that Simpson -- who had sported an increasingly prominent baby bump -- was expecting her first child dated back to late summer. She has said she learned she was pregnant on September 12.

Fashion Star will premiere tonight at 9:30PM ET/PT on NBC.