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Jessica Simpson has a big reason to be serious about her weight loss: she's getting ready to walk down the aisle.

"Knowing that I have the wedding coming up is an incentive to stay on Weight Watchers, count my points and stay in the gym," Simpson said in a Weight Watchers video on People.com. "I mean, when you see my dress, you'll know!"

Simpson, 33, got engaged to former NFL player Eric Johnson in 2010, and since then, the couple has welcomed a daughter, Maxwell, 20 months, and a son Ace, 6 months.

"The new year will definitely bring on the wedding bells, which is exciting," she said of finally marrying her longtime love. "I think it's about time!"

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To get back in shape, Simpson used Weight Watchers' two-week Simple Start program, which she said allowed her "to completely refocus and jump right back on track to weight loss and feeling amazing about myself."

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And though the singer is excited to say "I do" in a beautiful gown, she has smaller goals too.

"I'm just trying to feel good in a pair of jeans and T-shirt," she said. "I can't wait to be able to feel just comfortable in my skin and know that I'm back to the person I've been before. I know this time I'm going to be so much stronger and so much more empowered, because I really earned it and I really got here, and took the steps to get here."