Heather Rae El Moussa is getting candid about her health.

The Selling Sunset star revealed she has been diagnosed with Hashimoto's disease, eight months after welcoming son Tristan with husband Tarek El Moussa. 

"I remember saying to my assistant, ‘I feel like I'm dead,'" Heather told Today in an interview published Oct. 26. "My brain was so tired. My body was so tired. I was exhausted all the time and no amount of sleep could make it better."

The autoimmune disease occurs when antibodies are created that attack cells in the thyroid, with possible symptoms including tiredness, weight gain and muscle weakness, per Johns Hopkins University.

The reality star said she started feeling some symptoms when she was four months postpartum and dreaded having to be on camera for her Netflix show and the HGTV show The Flipping El Moussas with Tarek.

"Filming was absolutely brutal," Heather continued, "because I could barely get out of bed."

At first, she chalked up her feelings to being a new mother, recalling, "I was like, ‘I'm probably just foggy because of mom brain.'"

 

However, when Heather's milk supply started varying daily, she decided to visit a lactation consultant and get blood work done. The 36-year-old was then told that her pregnancy triggered the autoimmune disorder.

"When she told me what I had, I was in total shock," Heather recounted, but added that since being prescribed medication, she is "feeling much better."

As it turns out, Tarek's ex-wife Christina Hall—with whom he shares daughter Taylor, 13, and son Brayden, 8—was also diagnosed with Hashimoto's in 2020.

The Flip or Flop alum shared that she suffered from brain fog and didn't feel well until she learned how to manage her health.

"Now I'm more in tune with my body," Christina told People at the time. "I know how to cope with stress and my Hashimoto's disease." 

And Heather, too, is managing the disease and staying focused on motherhood. Back in September, she took a moment to gush over her newborn and stepchildren.

"Happy #Nationalsonsday my sweet Tristan bear," Heather wrote on Instagram beneath snaps of Tristan and Brayden. "I am so honored to be your mom. You have made me a better person. There's nothing I love more than being a mama & bonus mama. These boys have made me more fulfilled than I could have ever imagined."

To see more sweet moments of Heather and Tarek with their baby boy, keep reading...

"First ever Easter with our bunny," Heather wrote on Instagram as her baby boy wore Janie and Jack. "Tristan's loving it so far and as if it couldn't get any cuter… look at his outfits." 

Heather marked Tristan's first month with a cute photo shoot.

Referencing their shared initials, Tarek captioned this father-son picture: "Two T's in a pod."

Reflecting on her baby's first month, Heather shared, "Last day of February and it's been a month of love, mamahood adjustments, work days from home, breastfeeding ups & downs, the best newborn snuggles, sleepless nights & lots and lots of family time."

Celebrating Tristan's 2-week-old milestone, Heather captioned this sweet mother-son portrait, "Baby Tristan Jay… the obsession is real. my little love."

"It's love week and we're definitely feeling it over here," Heather wrote on Instagram a day before Valentine's Day 2023. "Lots and lots of kissing, snuggling, skin on skin, and holding our lover boy… we can't get enough."

The Selling Sunset star joked that she's been in "mama hibernation mode" after welcoming Tristan.

Posting a picture of Tristan wearing a top reading "New to the El Moussa Crew," Heather wrote, "Mom life is staring at him non stop because I can't get enough. The moment I held him in my arms he became my world."

Tarek wrote alongside a photo of his older children with ex-wife Christina Haack: "OMG….I have 3 kids!!!! How did this happen?"

According to the couple, Tristan was born on Jan. 31, 2023, at 6:55 a.m. PT. He arrived weighing 7 lbs., 7 oz.

"Our baby boy is here," Heather and Tarek shared while announcing Tristan's arrival. "Mama & baby are happy, healthy, tired but doing well. Our hearts are so happy."

For the latest breaking news updates, click here to download the E! News App