Pop Singer, Jessica Simpson Shares The Post-Pregnancy Routine She’s Using To Get Back In Shape After Birthing 3rd Child

American Pop singer and a former MTV reality show star, Jessica Simpson is seriously stepping up her fitness with the goal of getting back in shape after having her third child.

The 39-year-old mother-of-three gave birth to daughter Birdie Mae on March 19, and after a tough pregnancy — which included some seriously swollen ankles — Simpson is working on getting back in shape.

Now that Birdie’s a few months old, Jessica just shared with PEOPLE.com what she’s been doing to get back in shape. She said:

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“I am working really hard right now. Its not easy at all, but I am determined to feel good. I have been doing a lot of walking-getting my steps in not only burns calories but it also helps me clear my head and get focused.”

Along with her daily steps — Jessica previously told PEOPLE that she tries to walk three miles a day with her husband, Eric Johnson, and kids.

Jessica is also making some adjustments to her diet. She told the publication:

“I am eating healthy, too-I discovered I really like cauliflower. Who knew it could be a substitute for almost anything?!”

The businesswoman started posting about her postpartum recovery soon after giving birth to Birdie. In May, seven weeks after her baby was born, Jessica shared a photo that showed her struggling to touch her toes.

“Just stretching it out in my rubber corset,” she jokingly captioned the shot. “The joy of postpartum ?”

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But beyond getting fit, Simpson is having a monumental year — along with Birdie’s arrival, she just announced that she’s writing a memoir — and she’s celebrating it as she hits 39 years old on July 10. She tells PEOPLE:

“I feel pretty good about 39!. It is definitely one of those numbers that makes you think about age — last year of the 30’s and all — but on most days I feel like I have earned it.”

In the weeks following Birdie’s birth, Simpson admitted to PEOPLE how adjusting to life as a mother of three wasn’t the easiest thing to do. She shared:

“Three is challenging. We are trying to get into the groove and make sure all three kids are getting equal attention … it’s more than a full-time job right now.”

Still, the star said she was soaking up every moment with her youngest child. She added:

“[Birdie] makes our family complete. Someone once told me to keep in mind that everything is a phase with infants and kids … trying to remember that fact and celebrate the small victories.”

As for how she handles some of the more chaotic aspects of parenting two children and a newborn? She joked:

“The other night, all three kids were crying at the same time, so I just joined in! Ha!.”

Kudos to Jessica for easing back into her post-pregnancy fitness routine!