Baby Ace is growing up so fast!

Jessica Simpson shared a cute snapshot of her 3-month-old son via Twitter on Saturday, Oct. 5.

The adorable photos, all black and white pictures, had "3 MONTHS" written on it and showed the blonde beauty holding Ace.

Celebrity Kids PHOTOS

The reality TV star and fashionista, who welcomed her second child on June 30, is officially working with Weight Watchers again to shed her baby weight.

Andy Amill, who is the company's VP of Media Sales, told MediaBistro in a new interview that the famous blonde has been welcomed back into the fold.

"We were thrilled to welcome Jessica back on the Weight Watchers program in August," a company spokesperson confirmed. "With a toddler on the run and an infant to look after, we know she needs a plan that’s simple and fits into her life along with the support that’s so important to moms with young children."

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In an interview with Us Weekly following her son's arrival, Simpson lashed out about comments that had been made about her pregnancy figure by those she described as "weight bullies."

"I will never understand why people give pregnant women such a hard time," she told the magazine. "We are creating a human life: I think we get every excuse in the world to eat a doughnut!"