They were ready to remove my appendix. But it wasn’t my appendix at all.

One night, almost a year ago, I started feeling a sharp pain in my lower abdomen.

At first I thought it was a reaction to gluten I may have accidentally digested (I have celiac disease), but the pain was different than that.

Then I passed out. As quickly as I stood up, I was back on the ground again.

A sea of black enveloped me so quickly, I didn’t even have time to register before waking up again. It was as if my body just shut down without any warning and then turned back on, only to be facing up at the ceiling.

I had only fainted a couple of times in my life so it was scary. Yet, my pain faded away soon after — so I went to bed, hoping it was a fluke.

Instead, I woke up early in the morning to renewed pain that was growing at an alarming rate. After I tried to stand up, I immediately passed out a third time.

Scared and in agony, I headed to the hospital with the help of my roommate. Almost immediately, doctors decided my appendix was inflamed and that I’d most likely need it removed.

I’m an American but I was living in Australia at the time on a Working Holiday Visa, so the idea of needing surgery so far from home was terrifying.

I laid there for hours, mentally preparing for surgery. Yet, despite my immense pain, continual testing found no signs of appendicitis.

I was to be monitored overnight and retested in the morning.

I was given fluids all night and fasted in case of surgery. My pain had dulled a bit, but I wasn’t sure if it was from the medicine finally kicking in or it actually going away.

It was scary, staying overnight in a foreign country without any close friends or family nearby. Not knowing how much staying overnight was going to cost if my insurance decided not to cover it led me to wonder if I should leave altogether.

Thankfully, when the blood tests once again showed no indication of appendicitis, it was decided I wouldn’t be having surgery.

It was then that a doctor explained to me how endometriosis can mimic the pain of appendicitis, which is what they believed had happened — an endometriosis flare-up if you will.

I had been diagnosed with endometriosis by my gynecologist in America previously, but I had no idea that it could present as appendicitis. I was confused but relieved.

When I share that I have endo, most people aren’t actually sure what it is.

While it’s a popular buzzword in the medical world these days, endometriosis’ actual definition can be confusing.

“Endometriosis occurs when tissue similar to the lining of the uterus begins to grow outside of the uterus, where it doesn’t belong.” Dr. Rebecca Brightman, private practice OB-GYN in New York and educational partner for SpeakENDO, tells Healthline.

“These out-of-place growths called lesions are stimulated by estrogen, a hormone naturally produced by your body, which can fuel a range of painful symptoms and inflammation throughout the month,” she says.

While some people are asymptomatic, Dr. Brightman explains that symptoms often include painful periods and sex, pelvic distress, and bleeding and spotting between (often heavy) periods, among other things.

When I arrived at the hospital, I had disclosed that my primary doctor at home believed I had endometriosis. At the beginning there was no reaction, as the doctors had almost tunnel vision toward a diagnosis of appendicitis.

When they determined that was most likely what was happening, I was told I needed to go to the nearby “women’s hospital” to get that checked out.

It felt very dismissive when the male doctor said that to me. Like, well, that’s a woman’s problem, so we can’t help you with that here.

It’s further complicated by the fact that many with endometriosis are “believed” to have it, but it’s not always confirmed — because it’s tricky to diagnose.

As Dr. Anna Klepchukova, chief science officer at Flo Health, tells Healthline: “Diagnosing endometriosis can be difficult and can include a pelvic exam and ultrasound to MRI. The most effective diagnostic method is a surgical procedure, such as a laparoscopy.”

I’ve never had a laparoscopy to confirm the existence of my endometriosis. However, multiple doctors have confirmed that my symptoms are in line with an endometriosis diagnosis, along with having a genetic link.

Since endometriosis is known to return, even after surgery, I haven’t taken the next step to have the tissue removed yet. Fortunately, at least most of the time, I’ve been able to manage my pain through birth control and medicine.

Endometriosis can also present as numerous other conditions, making it even more baffling for doctors and patients alike.

I’ve gone to the hospital at least 5 or 6 times in my life due to overwhelming pain near my appendix, with it not being inflamed any of those times.

While some of them were before my endometriosis had been diagnosed, even when I informed a doctor of my condition, they made no connection.

In each case, after determining that my appendix was fine, the doctors sent me home without taking the time to assess what had caused the problem in the first place. Looking back, if someone had just taken the time to further evaluate what might have been wrong with me, I could have been saved from a lot of pain and frustration.

That in and of itself adds to the frustration even more. Why did no one take the time?

“Endometriosis is considered ‘the great masquerader’ because it mimics so many other disease processes. It has been reported to take 6 to 11 years for an endometriosis diagnosis,” says Dr. Mark Trolice, OB-GYN, reproductive endocrinologist and director of Fertility CARE: The IVF Center.

“Often [patients] first see their primary care physician, whose first course of action typically is nonsteroidal anti-inflammatory medication. If the patient cites painful intercourse and periods as symptoms, [they] will usually be referred to a gynecologist, who often prescribes birth control pills,” Dr. Trolice continues.

“The delay is especially seen in adolescents who may not stress their level of pain since they are new to menstruation.”

I was released from the hospital and instructed to see an ‘expert.’ As I was in Australia, that was easier said than done.

In the end, I went to a primary care doctor who specializes in endometriosis cases. She instructed me to go on the FODMAP diet for a few days after my period each month. This diet stops you from eating foods with high acidity, among others, that may trigger a reaction from endometriosis.

“Many [will] opt for less invasive treatments, such as taking hormonal medications, including oral contraceptives and some IUDs, [which] are proven effective in treating endometriosis and providing pain relief,” says Klepchukova.

As with anything, she adds, what works best for one person may not be the right choice for another.

I haven’t experienced another flare-up on that scale since. The doctors believed I passed out from stress on my body — both mental and physical — when facing the pain.

Now that I know how easily endometriosis can manifest as other conditions, I’m even more determined to keep it under control.

At the same time, research must continue so that people don’t have to continue suffering through a decade or more of pain before being diagnosed.

For starters, a very painful period and other distressing menstrual symptoms can no longer be dismissed as “normal.” Pain must not be minimized or ignored.

For so long I felt weak if I had to miss school or when I was hunched over in pain from my endometriosis. But this is a debilitating disease that affects so many people — all too often without them knowing.

The only person who decides how bad pain feels is yourself.

As Rachel Greene said in “Friends”: “No uterus, no opinion.” It’s severe pain that shouldn’t be dismissed by anyone else, especially someone who hasn’t experienced it themselves.

If you’re experiencing any symptoms you believe could be endometriosis, don’t ignore them or let any medical professional dismiss them. No one should have to stay in pain. We deserve so much better.

Sarah Fielding is a New York City-based writer. Her writing has appeared in Bustle, Insider, Men’s Health, HuffPost, Nylon, and OZY where she covers social justice, mental health, health, travel, relationships, entertainment, fashion and food.