Credit: FameFlynet

Kristin Cavallari is going to be one chic mama!

Just one day before announcing she and on-again fiance Jay Cutler were expecting, the pregnant former Hills star stepped out to grab groceries in West Hollywood, Calif., Saturday wearing super sexy skinny jeans, a beige blouse and matching heels.

Although she hid her eyes under a pair of aviator sunglasses, it is clear the beaming star was on cloud nine. "She is really happy. She is in the early stages, but she can't wait to be a mom," a source tells Us Weekly of mom-to-be Cavallari, 24.

Though Cavallari and NFL player Cutler, 28, just announced their baby news to the world, the insider says close friends and family have known about their "surprise" pregnancy for a few weeks.

Despite calling off their engagement in July 2011 after just three months, the couple -- who were introduced by E! News host Giuliana Rancic in 2010-- reunited in November 2011 and couldn't be more in love.

"[Jay] absolutely adores her, he worships the ground she walks on and she is so in love with him," says the source. "This is a real match, they are made for one another. Everyone is so happy that they are going to have a baby together. She's going to be a great mom."