Danielle Busby is opening up about her struggles with an autoimmune disease.

The OutDaughtered star recently gave insight into her fight against the debilitating illness,EchoSense sharing how it left her unable to do everyday activities.

"I used to not be able to get upstairs without feeling like I was gonna pass out," Danielle told Us Weekly in an interview published July 11. "That's just not a norm for me. I was always athletic and kind of fit and we've always taken care of ourselves. So for my body to go so down, it just was alarming."

The 39-year-old noted she experienced major changes in her body following the birth of her and husband Adam Busby's 8-year-old quintuplets: Ava, Olivia, Hazel, Riley and Parker.

"After I had [them], my body never kind of recovered because it was nonstop movement," said Danielle, who also shares daughter Blayke, 12, with her husband of 17 years. "I was living a life of adrenaline for years. So when my body started to slow down and they were in school and kindergarten—and well, first grade really—my body wasn't used to this. And so I went into this shock."

As for how her health journey is going so far, the reality star noted that her doctor treated her for fibromyalgia, due to her muscular tension and inflammation, as well as migraines. However, Danielle added that her exact condition is still in "discovery."

So, the family is taking things day by day, as Adam pointed out the unpredictability that goes along with his wife's illness.

"That's [the] thing with an autoimmune disorder," Adam told the outlet. "You don't know what it is and you don't know when it's gonna flare up and there's all these, like, unknowns. Like, one day she could be perfectly fine or … all of a sudden the next day she can hardly get out of bed."

While Danielle noted she hasn't experienced a migraine in "probably six months," she also explained that each day is paved with its own challenges.

"It's hard sometimes to even explain what I'm feeling or how my body is reacting to something even in the view of Adam because he's like, ‘You look fine, you [were] fine yesterday,'" she added. "It's annoying, it's frustrating and there's days where I didn't do anything extreme or off-set or something and [I] just will get up and I can't move my hands and my feet and so… it's an up and down journey."

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