One woman is sharing her story to help millions of others.

“You’re fine.”

“It’s all in your head.”

“You’re a hypochondriac.”

These are things that many people with disabilities and chronic illnesses have heard — and health activist, director of the documentary “Unrest” and TED fellow Jen Brea has heard them all.

It all started when she had a fever of 104 degrees and she brushed it off. She was 28 years old and healthy, and like many people her age, she thought she was invincible.

But within three weeks, she was so dizzy that she couldn’t leave her house. Sometimes she couldn’t draw the right side of a circle, and there were times when she was unable to move or speak at all.

She saw every kind of clinician: rheumatologists, psychiatrists, endocrinologists, cardiologists. No one could figure out what was wrong with her. She became confined to her bed for almost two years.

“How could my doctor have gotten it so wrong?” she wonders. “I thought I had a rare disease, something that doctors had never seen.”

That’s when she went online, and found thousands of people living with similar symptoms

Some of them were stuck in bed like her, others could only work part-time.

“Some were so sick they had to live in complete darkness, unable to tolerate the sound of a human voice or the touch of a loved one,” she says.

Finally, she was diagnosed with myalgic encephalomyelitis, or as it’s commonly known, chronic fatigue syndrome (CFS).

The most common symptom of chronic fatigue syndrome is fatigue that’s severe enough to interfere with your daily activities, that doesn’t improve with rest, and lasts for at least six months.

Other symptoms of CFS may include:

Like thousands of other people, it took years for Jen to get diagnosed.

According to the Institute of Medicine, as of 2015, CFS occurs in about 836,000 to 2.5 million Americans. It’s estimated, however, that 84 to 91 percent haven’t been diagnosed yet.

“It is a perfect custom prison,” Jen says, describing how if her husband goes for a run, he might be sore for a few days — but if she tries to walk half a block, she might be stuck in bed for a week.

Now she’s sharing her story, because she doesn’t want other people to go undiagnosed the way she did

That’s why she’s fighting for chronic fatigue syndrome to be recognized, studied, and treated.

“Doctors do not treat us and science does not study us,” she says. “[Chronic fatigue syndrome] is one of the least funded diseases. In the U.S. each year, we spend roughly $2,500 per AIDS patient, $250 per MS patient, and just $5 per year per [CFS] patient.”

When she started speaking up about her experiences with chronic fatigue syndrome, people in her community began reaching out. She found herself among a cohort of women in their late 20s who were dealing with serious illnesses.

“What was striking was just how much trouble we were having being taken seriously,” she says.

One woman with scleroderma was told for years that it was all in her head, until her esophagus became so damaged that she will never be able to eat again.

Another with ovarian cancer was told that she was just experiencing early menopause. A college friend’s brain tumor was misdiagnosed as anxiety.

“Here’s the good part,” Jen says, “despite everything, I still have hope.”

She believes in the resiliency and hard work of people with chronic fatigue syndrome. Through self-advocacy and coming together, they’ve devoured what research exists and have been able to get pieces of their lives back.

“Eventually, on a good day, I was able to leave my home,” she says.

She knows that sharing her story and the stories of others will make more people aware, and might reach someone who has undiagnosed CFS — or anyone struggling to advocate for themselves — who needs answers.

Conversations like these are a necessary start to changing our institutions and our culture — and improving the lives of people living with misunderstood and under-researched diseases

“This illness has taught me that science and medicine are profoundly human endeavors,” she says. “Doctors, scientists, and policymakers are not immune to the same biases that affect all of us.”

Most importantly: “We need to be willing to say: I don’t know. ‘I don’t know’ is a beautiful thing. ‘I don’t know’ is where discovery starts.”

Alaina Leary is an editor, social media manager, and writer from Boston, Massachusetts. She’s currently the assistant editor of Equally Wed Magazine and a social media editor for the nonprofit We Need Diverse Books.