StormFinch, I went through hell, and many doctors and dentists, years ago to try to find out why I was having almost constant crippling migraines. I was suicidal, it was so bad. X-rays and EEGs and drugs that crippled me even more than the pain. Then I realized a correlation between my cycles of headache and cycles of discomfort from my wisdom teeth trying to errupt. So I went against the recommendations of two dentists and had my wisdom teeth surgically removed. (The surgeon asked why I had waited so long - there was absolutely no way those teeth could come in and they were trashing my jaw.) Migraines gone. Clear gone, didn't come back.
I understand your thyroid issues. My mother and two sisters had atypical thyroid disease. Went to the doctors, got the tests, everything just fine, ma'am, you don't have a thyroid problem. Until one sister ended up in a locked psych ward and the other in emergency surgery. Mom, fortunately, got proper treatment from the start.
So many times, I or someone in my family went to the doctor and had their symptoms shrugged off. I had horrible tendonitis in my wrists after my daughter was born. I could barely lift her. Two doctors told me it was probably arthritis, nothing to do about it, before I found one that properly diagnosed and treated it. Later, in mother's groups, I found out that this is a very common occurrence in new mothers, the other mom's saying things like, "Oh, yes! I had that, too. My wrists hurt so badly!" It makes sense - pregnancy hormones soften the tendons and ligaments, then the hormones change and you're lifting and holding a baby 24/7 with your palm up flat. Not one of the other mom's who had the same symptoms had gotten anything more from their doctors than the same shrug and oh it's probably arthritis.
It would be nice to be able to get good medical treatment, but for most people, it's difficult, if not impossible, to find and to afford. So I think of my doctor as the guy who writes me a prescription once I figure out what's wrong with me and tell him what it is. And he's one of the good ones.
My ex-husband finally went to the doctor for his tinnitus at my urging. He was diagnosed with tinnitus. It's so common and has so many causes, that you have to do your own detective work.