NEWPORT BEACH, CALIFORNIA: Heather Rae El Moussa has been diagnosed with Hashimoto’s disease aka Hashimoto's thyroiditis, an autoimmune disease that affects the thyroid gland, as per the National Institute of Diabetes and Digestive and Kidney Diseases.

In an interview with Today, the 36-year-old 'Selling Sunset' star opened up about dealing with symptoms of fatigue and the subsequent journey to her diagnosis.

Heather, who is a realtor by profession, said she felt so tired that she didn't even want to film her reality television shows, namely, HGTV’s 'The Flipping El Moussas', on which she features alongside her husband, Tarek El Moussa, and Netflix's hit series, 'Selling Sunset'.

Heather Rae El Moussa initially thought she had 'mom brain'

In the interview, Heather Rae El Moussa recalled, "I remember saying to my assistant, ‘I feel like I’m dead'. 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."

She added, "Filming was absolutely brutal because I could barely get out of bed."

Initially, the seasoned businesswoman assumed she had "mom brain" and was feeling fatigued because she had just given birth to her first child, Tristan, in January this year.

Heather is also a doting stepmother who’s helping raise her stepkids, Taylor, 13, and Brayden, 8, whom Tarek shares with his ex-wife, Christina Hall.

However, when Heather realized all of a sudden that she was unable to produce enough breast milk for her newborn, she figured something else might have been ailing her. And she would be proven correct in her assumption.

After carrying out bloodwork, she was diagnosed with Hashimoto’s disease, which caused her lack of energy and reduced breast milk production. As per Heather, it was likely triggered by her pregnancy.

Heather shared that she was in "total shock" when she was diagnosed, but at present, she’s been "feeling much better."

Heather Rae El Moussa's baby Tristan has had a difficult year

While Heather Rae El Moussa has been preoccupied with a health situation of her own, little Tristan was born with a tongue tie, a medical condition in which the band of tissue connecting the tongue to the floor of the mouth is thicker, thus preventing optimum tongue movement.

The tongue tie made it all the more difficult for Tristan to breastfeed, although his condition was swiftly and painlessly corrected with the help of laser surgery.

"We had a lot of things working against us, including my autoimmune disorder, but we did it," stated Heather.

Heather Rae El Moussa threw shade at 'Selling Sunset' for Season 7 cast photo snub

Heather Rae El Moussa announced her diagnosis just a few weeks after she spoke about being cut off from the full cast image for ‘Selling Sunset’ Season 7.

She took to Instagram and wrote, "Looks like I got pushed in the water… its a good thing I can swim! Congrats to my girls on S7! 💗 You may see me in a few episodes….. 💁🏼‍♀️."

Previously, Heather hinted at the possibility of her not returning to the Netflix show after not being asked to film post-maternity leave, saying, "Season 7 is filming right now, but I’ve been off maternity leave and I’ve been excited to get back to work and so far I have not been called back,” she said in March, this year."