Credit: ABC News.

Jessica Simpson officially unveiled her post-baby body on the premiere of Katie Couric's talk show today, saying that losing her pregnancy weight has been a "lot of pressure" and a "challenge."

"During pregnancy, I didn't really think about it," she said about her weight gain. "I thought my doctors were telling me that it was just a lot of water and whenever my water broke my whole entire stomach would go down but that did not happen. All the weight did not come out with the baby."

Simpson said she's lost more 40 pounds since giving birth to Maxwell Drew Johnson in May. She previously said she weighed 170 pounds when she posed nude and pregnant for the April issue of Elle magazine. She is 5-foot-4.

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Earlier this year, Simpson signed a reported $3 million dollar contract to be the celebrity face of Weight Watchers. She said she's 10 pounds away from her goal weight, and she's using her daughter to get there.

"I basically take her with me, whether it's strapping her on me or strolling around the neighborhood," she said. "My new goal is 14,000 steps a day."

But food cravings are still an obstacle.

"I feel like what made me eat more is my hormones and breastfeeding. I've never wanted chocolate more in my life," she said. I've had to really stay focused and focus on my diet and concentrate on what I'm putting in my body."

Watch Jessica Simpson guest host "Good Morning America" Tuesday morning starting at 7 a.m. ET.