January 22, 2015 12:15 PM

Break out the blue balloons: It’ll be a second son for Marisa Miller.

“We found out we are having another boy and I’m so excited!” the model mama, who’s expecting her second child with husband Griffin Guess in late spring, tells PEOPLE exclusively.

After growing up with two sisters, Miller was looking forward to giving the couple’s 2-year-old son Gavin Lee a sibling — and even more ecstatic after learning the sex of their baby on the way.

“It will be awesome for Gavin to have a buddy,” she says. “I never had brothers so raising a boy has been awesome. Gavin is so funny and I get to be silly all day with him.”

Courtesy Marisa Miller

Miller, 36, had a rough start to her second pregnancy — “I was really nauseous and could only handle eating bagels,” she says — but she’s back on track with her healthy habits. “Right now, I’m feeing great!,” she shares, adding she’s eating clean and doing Pilates three days a week.

“This pregnancy has been very different because I’m also chasing around a toddler, so you can’t really lay down if you feel sick or tired,” she explains. “But I also feel a lot less anxious about what’s to come.”

While her first pregnancy was filled with hours of researching “labor, breastfeeding and thinking about every little detail,” Miller admits, these days, her time is spent focusing on the present.

“I’m too busy having fun with Gavin to worry,” she says. “I’m a little nervous about the newborn stage and how sleep deprived you get, but more than anything, I just feel so blessed to have a healthy baby and pregnancy so far.”

— Anya Leon

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