Kristin Cavallari: 'Having a Baby Is So Much Fun!'

Motherhood agrees with Kristin Cavallari.

Two months after giving birth to son Camden Jack -- her first child with fiance Jay Cutler, 29, quarterback for the Chicago Bears -- the 25-year-old reality TV star is happier and hotter than ever. Us Weekly caught up with the new mom at Friday's Bing It On Halloween Costume Challenge in New York City, where she got into the spirit of the season by trying on bunny ears, a sailor hat, and a Minnie Mouse headpiece.

"Jay and I are being really boring and not dressing up [for Halloween], but we're going to dress up Cam as a lion," she revealed. "He's a Leo, so I thought that would be really cute."

PHOTOS: Kristin's chic pregnancy style

Wearing a sheer blouse, eggplant-colored shorts, and nude Christian Louboutin pumps, the former Hills star showed off her svelte post-pregnancy body and gushed about her little boy, whom she affectionately calls "Boo Boo."

"I put on 25 pounds [while pregnant], and last time I weighed myself, I had four pounds to go," she told Us. "I'm guessing I've lost about two pounds [since then], so I probably have two more pounds until my pre-baby weight."

Cavallari insists there's no big secret to her success, though. Since giving birth on August 8, she simply eats healthy -- seaweed salad and vegan cookies are among her favorite snacks -- and stays active.

"I breastfeed, so that alone burns 500 calories. I also walk the treadmill," she said. "Nothing too crazy."

PHOTOS: Jaw-dropping post-baby bods

Life is crazy enough as it is. Asked whether she had thought about her pending nuptials to Cutler, the busy mom replied: "I'm too busy with Camden to even think about planning a wedding. And I want Camden to walk down the aisle, so we'd have to wait anyway for him to start walking."

And though she said she "definitely" wants more kids, she's not looking to expand her brood just yet. "I don't want to start trying for another child until Camden is at least one year old," Cavallari explained to Us.

In the meantime, she has her hands full. With hubby-to-be Cutler often away for work, the first-time mom admitted to occasionally missing her "alone time." But motherhood has definitely changed her for the better, she said.

PHOTOS: Kristin's best bikini moments