Reese Witherspoonis getting candid on how motherhood changed her life.

“I’ve been a mom since 1999,” Witherspoon revealed. “I got pregnant when I was 22 and delivered when I was 23.”

Witherspoon is mom to daughterAva Elizabeth, 20, and sonDeacon Reese, 15, with ex-husbandRyan Phillippe. The actress also shares sonTennessee James, 7, with husbandJim Toth.

While she’s certainly gotten the hang of parenting now, Witherspoon admitted she “was scared” in the beginning.

“I didn’t know what it was going to do to my job, my career,” she shared. The year Witherspoon gave birth to Ava, she starred in the filmsElection,Cruel IntentionsandBest Laid Plans.

It wasn’t until after welcoming her daughter that she realized “your entire life will change.”

“Everything you believe. Everything you eat. Every piece of independence you have. You can’t go out without thinking about another person,” Witherspoon said.

“You don’t sleep anymore,” Witherspoon continued, adding that this was her experience at the beginning, explaining “it evolves from there.”

The actress went on to admit that she’s “glad” she had kids at a young age because “having little kids is more physical and it’s really hard on your body.”

Witherspoon gave birth to son Deacon at age 27 and had son Tennessee 10 years later.

The star shared that when it came to juggling her career and motherhood, she relied on a strong support system.

When she first became a mom, Witherspoon’s own mother didn’t live in the same city as her, so she joined a yoga group for women — who she still calls on today.

Reese Witherspoon and children Ava and Deacon Phillippe.Steve Granitz/WireImage

Reese Witherspoon and kids Ava Phillippe and Deacon Reese Phillippe

“I depend on the kindness and support of my mom friends,” Witherspoon shared. “It’s really about your support system, your family structure.”

“Being a mom is really great, it’s a big part of my life. I would say it’s the biggest part of my life.”

Witherspoon’s advice comes on the heels of her son Tennessee’s7th birthday.

The actress wished her youngest a happy birthday with a few sweet Instagram posts on Thursday.

“Boy, this kid makes me laugh! Happy 7th birthday to my sweet boy Tennessee,” theBig Little Liesstar wrote in a caption underneath aphotoof the mother/son pair. “Here’s to a day filled with chocolate cake, Beyblades and dog cuddles! 🎈#thisis7.”

In the picture, Witherspoon wears a straw hat and a dark blue denim shirt, accented with dainty gold bracelets, necklaces and earrings. She appears to be caught mid-laugh as Tennessee, wearing a white and blue striped polo shirt, gives a smile to the camera.

On herInstagram Stories, Witherspoon shared some fun moments from Tennessee’s special day.

She shared a video of birthday decorations, including a large gold “7” balloon and “happy” garland. Then she showed off what Tennessee is loving these days: “lots of hexbugs” and “so many beyblades!”

Michael Kovac/Getty Images

Jim Toth, Reese Witherspoon

Last month, Witherspoon spoke on the more difficult aspects of parenting — likegetting school supply lists at the very last minute.

The Draper James founder explained in another Instagram post in late August that she communicates with her three kids on Snapchat, featuring asilly selfie, in which she looks shocked with a Snapchat filter over her face.

“Are you seriously telling me TODAY about all the school supplies you need tomorrow?” she wrote atop the photo. In the caption, she added, “How to talk to your kids on snapchat… the filter adds a much more serious tone, don’t you think? 📚 #momlife #backtoschool.”

But Witherspoon can’t juggle her many projects and three kids without a little help from a very relatable source.

“Coming to you this Thursday to remind y’all that behind every successful woman is a strong cup of coffee and a pair of practical ( and cute 😉)shoes. ☕️👟,” she wrote in anInstagram captionfor a photo from the set ofLittle Fires Everywhere, in which she stars oppositeKerry Washington.

source: people.com