Sleepless in The Hills!

After welcoming son Camden Jack three weeks ago with fiance Jay Cutler, Kristin Cavallari hasn't been getting much beauty sleep.

PHOTOS: Kristin's maternity style

The 25-year-old former Hills star tweeted Thursday, "Rough night last night! Little guy just didn't want to sleep until about 4am."

Baby Camden is the first child for Cavallari and the Chicago Bears quarterback, 29. The couple revealed they were expecting back in January, two months after announcing their nuptials were back on following a July 2010 split.

PHOTOS: Most memorable Hills moments

On Aug. 10, two days after her son was born, Cavallari tweeted, "Being a mom is the most incredible feeling. I am so in love with this little boy!"

But there have been a few challenges since then!

"Cutting a newborn's nails might be the scariest thing ever," she observed on Twitter last week.

PHOTOS: Kristin's bikini bod

The new mom is, however, savoring her favorite foods once again. One fan asked on Twitter, "Have you had your 'post-pregnancy sushi' yet?" Cavallari replied, "In the delivery room! Ha!"

This article originally appeared on Kristin Cavallari Has a "Rough Night" With Baby Camden