Karlie Kloss Says Son Levi 'Forever Changed My Life' as She Celebrates His Third Birthday

Karlie Kloss is celebrating her little guy's big day.

On Monday, the supermodel, 31, shared a carousel of photos on Instagram in honor of her son Levi's third birthday. Kloss included sweet photos of her son holding birthday balloons, reading books, enjoying the outdoors and spending time at Coney Island.

"3yrs ago today, you forever changed my life and I couldn’t be more proud and humbled to be your mom," Kloss wrote in her caption. "Thank you for making me a mommy. happy birthday Levi, thank you for choosing me and @joshuakushner. We couldn’t love you more.✨🤍🎂✨."

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Kloss shares Levi and son Elijah, 8 months, with husband Joshua Kushner.

Speaking with PEOPLE in November, the Kode with Klossy founder said the one thing that she couldn't control during her pregnancy with Elijah was her posture.

"Just being pregnant for nine months, I found my posture got so bad," she shared. "So now I'm relearning my whole anatomy and trying to fix it, straighten my back." Her fitness routine has also changed with her becoming a mom.

"My routine has evolved. It's gotten more efficient. I feel like my philosophy has gotten much more about strength in sustainable ways. So I do light weights and also body weight exercises. I travel a lot still, so I don't always have a gym nearby," Kloss explained.

"So I like to do things that I can do anywhere. And I like to squeeze in the workout first thing in the morning. Actually, the first thing I do in the morning is check my sleep data," she continued. "I'm weirdly competitive with myself over my sleep."

She previously shared with PEOPLE about how her pregnancies had resulted in a greater love for herself.

"I had a conversation with myself a while ago because I want to be in shape, but I also have more self-compassion because my body created life." While marking her son's birth on Instagram in August, Kloss echoed the same sentiments.

She wrote next to a photo with her sons, "Going into 31 with a heart full of gratitude 🙏💛✨."