The former reality star talks about juggling work and being a mom to three young children

Kristin Cavallari is a mom, actress, style icon — and cover star!

For the June 2016 issue of Modeliste Magazine, the 29-year-old former star of The Hills and Laguna Beach dished on her new book Balancing in Heels, and her life as mom to sons Jaxon Wyatt, 2, and Camden Jack, 3½, as well as daughter Saylor James, 6 months.

“I think the hardest part of being a working mom is that I miss my kids a lot. I live in Chicago, but my work is always in New York or L.A., so I always have to travel for my job,” says Cavallari, who has been married to Chicago Bears quarterback Jay Cutler, 33, since 2013.

She adds that FaceTime “helps a lot,” and that “when you finally have kids, you realize how selfish you are. I think we are naturally selfish beings. When you have kids, that can be kind of a shock at first.”

Kristin Cavallari Modeliste June 2016 1

Dorit Thies/Modeliste

Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.

But that doesn’t mean the mom of three doesn’t still try to prioritize “me time” — it’s just a bit more challenging nowadays.

“I think just trying to make time for yourself is very hard,” she says. “Especially now that I have three [kids], finding that time can be very difficult.”

But it’s all worth it for Cavallari, who says that the most rewarding part about having kids is how much her love has multiplied.

“There’s just so much more love in your life. I finally feel like I have a real identity,” the model and author says. “I feel like I have a purpose here in life now. I’m a mom to these three amazing little babies, and my whole world just kind of opened up.”

Kristin Cavallari Modeliste June 2016 1

Dorit Thies/Modeliste

As far as how the super-fit Cavallari stays in shape while juggling a jet-setting career, a marriage, and parenting duties to three children age 3 and under?

“I work out with a trainer three to four times a week, and I just do weight training. I don’t do any cardio,” Cavallari says. “For me, it’s just about building muscle and maintaining the little muscle that I have.”

She adds, “The more muscle you have, the more fat you burn.”

Kristin Cavallari Modeliste June 2016 1

Dorit Thies/Modeliste

The nutrition-conscious Cavallari confesses that she “loves to cook” for her family so much that she does so almost every evening.

“I’m really hoping to do a cookbook,” she says, adding that though she does splurge from time to time, “90 percent of the stuff that [she makes] would be healthy.”

And of course, her family — which she has said in the past she is done growing — is first on her list of items she’d bring to a deserted island. The other two? Tunes and protection from the sun.

“I need music in my life … and probably a hat, because I wouldn’t want to get sunburned,” she says.

Jen Juneau