I know what you mean.
For the past four years I have had a groin injury that limits my ability to exercise. It is not a "really big deal" but after about three miles of walking, it becomes painful and swollen. The pain persists after I get home and sometimes spikes such that I yelp in pain.
Before my diabetes diagnosis, it was really the only health issue that I was working on. At this point I have lost track of the specialists I was sent to but they included at least: a hernia specialist, an orthopedic surgeon, back to the hernia specialist, then to another orthopedic surgeon, and finally a round of physiotherapy. Oh, and a podiatrist, who found that one leg is longer than the other and prescribed orthotics.
This being America, along the way I paid out thousands of dollars for tests and so forth (even after the insurance company's payments). I had a cat-scan and two MRIs. They stuck needles into my muscles, tried all sorts of things.
The end result? Nothing. One after the other, they admitted that they had no idea what the problem is, and all the tests were negative. The only thing that helped was the physiotherapy, which does not reduce the swelling but helps deal with the pain, mainly by strengthening the neighboring muscles and therefore taking stress off the injured area.
I have now reconciled myself to just living with it for the rest of my life. The course of physiotherapy is over, but I continue to do the exercises every day at home, and they are helpful.
Doctors seem to be "totally at sea" when they are unable to tick a checkbox for a known, obvious condition. I suppose this is quite understandable but the frustration for the patients is almost unbearable sometimes.
Oh, and I also hate some of their metrics. What does, "Rate your pain on a scale of 1 to 10" mean? When they asked about my groin pain, I said, "it starts at around 2 and goes up to 5." Immediate loss of interest by doctor. You see, to me, "10" would be having the Gestapo tear out your fingernails while simultaneously applying electricity to your private parts. I bet I could have got the doctor's attention if I had said "10" but I'm just not inclined that way.