Molly Sims Changes Her Mind About Keeping Baby's Sex a Surprise: We Have a List of 'Weird' and 'Cool Names'

It’s almost time for baby Stuber to join the world and Molly Sims is feeling it!

The pregnant mother of two caught up with PEOPLE about how her third pregnancy is going and admits that it’s been harder this time around.

“We’re seven months, we’re getting down to it and I’m starting to feel tired. Starting to feel it again, let me tell you,” the mom-to-be admits to PEOPLE. “Maybe it’s because I have two other kids, but I’m definitely feeling it.”

Sims and her movie producer husband, Scott Stuber, are already parents to 4-year-old son Brooks Alan and 19-month-old daughter Scarlett May — making things a little more challenging this time around.

“When you have no kids, you can nap, and then you have one kid and you’re still napping — and then no,” the 43-year-old says. “Someone’s always on, whether it’s Brooks or Scarlett. I mean, it’s so fun, but it’s game on!”

Although the little one on the way was a surprise for the family, Sims says they’re deep into the name picking process even though they don’t know the sex of the baby yet.

“We originally weren’t gonna know, but now we’re gonna figure out what it is,” the model says. “We have our list of boy names and girl names and weird names and cool names, but we haven’t agreed on anything.”

RELATED VIDEO: Molly Sims: I gained 85 lbs. during her first pregnancy

Another decision coming down to the last second is the baby’s nursery — a task the model admits she’s a “tad” late on planning.

“I just started, I’m a little late,” says Sims. “We’re looking for something neutral. It’s going to be either an orange or a citron yellow, which I love. We’re keeping it more modern.”

And although they don’t know the sex yet, one person “dying” for the baby to be a boy is big brother Brooks, whom Sims says is obsessed with her bump.

“He kisses my belly every night,” the proud mom says of her firstborn. “We had a doctor’s appointment yesterday and he wants to see the pictures and every day he asks me when it will be here. He is very excited, to say the least.”

As for the mom-to-be, Sims has partnered with Nature’s Bounty to make sure she takes care of herself throughout the pregnancy and beyond.

“I’ve been a proponent of prenatal ever since I was 30 and my hair broke off from Vegas,” Sims says. “Then I started taking Nature’s Bounty Hair, Skin and Nails Gummies because they had biotin in them and I could take them while I was pregnant. I talked to my doctor and she said it was totally fine, so I combined the two and I’m going to combine the two for a long time after.”