I've had POTS since I was a kid, and had mostly gotten over it by age 21. So it wasn't in the forefront of my mind when I began experiencing a pulsing, stabbing pain in points all over my body a little over a year ago. After being diagnosed with Lyme and then fibromyalgia by four different doctors, I went back to my childhood neurologist, Dr. Rowe at Hopkins. He disagreed with the fibro diagnosis, and had me get an MRI.
That MRI revealed a retroflexed odontoid that pushes my top vertebra forward, kinking my spinal cord and putting significant pressure on my brainstem (which is also hanging out of my skull for some reason). A later CT revealed that this is all due to ligament degeneration, which is now apparent in most joints (snapping/popping, loose knees, incredible back pain).
Learn from this. If a doctor gives you a diagnosis that doesn't seem quite right, question it. I had a second opinion, a third, and a fourth, all in different specialties. They all missed it. As a result, over the past year I have started distrusting my own perception of my body. But they were wrong, and if I hadn't continued my search because it was "just fibro," I never would have found the real cause of my symptoms until it was too late. It's been a terrible year of pain, but now I understand my situation and am able to act accordingly by booking PT, neurosurgeons, and geneticists until I find the right combination.
So please, trust your gut. Know that your experiences and pain are real, and deserve to be treated as such (even if people can't see them). And if you get a catch-all diagnosis like fibromyalgia, rule out absolutely everything else before you settle.