This has been my experience too, unfortunately. But, hey, at least your doctor straight-out asked you what tests you wanted. I had to argue with mine just to get to that point.
For most of my life I’ve had episodes of tachycardia, intense nausea+vomiting, severe muscular weakness and dizziness happening seemingly randomly sometimes after physical exertion or exposition to cold. I’ve had an abnormally early puberty with almost absent secondary sexual characteristics. Also, at times my limbs become paralysed, unable to move at all except for breathing and talking, it usually happens after resting.
The crises receded in my 20s when I became prediabetic and grew very fat, and came back with a vengeance after I followed a very low carb diet in my 30s, lost the extra weight and suppressed my HbA1c back to healthy level. In a few of those ‘new and improved’ crises I almost died, so I firmly committed to finding an explanation and possibly a cure. The occasional paralysis also came back.
I went to my GP who prescribed a dozen blood tests, then some more, and then assumed it was all in my head somehow. After more arguing and disproving some of his false assumptions (mostly about my character and reactions to stress) he grudgingly dismissed me to an endocrinologist. I thought I was making progress at last.
The endo swept most of the lab tests aside and just assumed that I was overdosing on vitamin D (which I only had been supplementing in the previous winter months). So I stopped all vitD and saw no improvement on the crises’ front.
I talked about all this to a (rather unorthodox) psychotherapist, in case it really was in my head all along, and this guy suggested instead it might be some rare genetic disease at play. He then asked for a second opinion from a friend of his, a surgeon with a fondness for puzzles, who accused me of either being insane or of lying about my symptoms and lab results – because it all made no sense to him and he had no answer.
I never held the medical profession in any special regard to begin with, to me they’ve always been highly-trained workers with heads full of precious, specific knowledge but with little wisdom to connect it all and make sense of it except in the most common clinical cases. But even if I had special consideration for them, I’d have certainly lost it after all this, because they’ve been right next to useless. All the useful data I got so far came from blood tests I had to pry from them with pointy words, all their proposed treatments failed, all their explanations conflicted with already present evidence. It’s like they have no curiosity at all, and little training in actual science – as in epistemology = the proper way of forming beliefs from objective reality.
To think that there are millions of people like me, all with all kinds of rare diseases that all these doctors know little or nothing about, that the medical profession fails to help in the same way, is rather unnerving.
To this date, and all on my own using the Internet, some dangerous self-experiments and my college training in science, I have finally figured out diet adjustments that really do work for me, preventing the crises and drastically reducing the frequency and severity of the paralysis episodes. It consists of avoiding a long list of food items, and gobbling salt by the gram nearly every day. I’ve had zero crisis since.
The websites that actually helped me: support groups' forums for people with CAH and Addison's disease (neither I have though... mine might be pseudohypoaldosteronism type 1, except it’s unusually mild and with a late onset, and covers only half the symptoms), Wikipedia's trove of pages about steroidogenesis and associated disorders, and several obscure publications on PubMed about specificities of organ-specific aldosterone receptors and the genetics thereof.
At this point the “proper” thing I should do is find a geneticist and confirm the suspicions of having some unclear, maybe unknown, rare disease, or just keep doing my stuff and disregard medical “help”. And the former really looks like a waste of time and money... I've just sent a DNA sample to 23andme as a stab in the dark, I'm waiting on the results now.