Alas I am living that. I did my homework I have worked out what I want to do next and I am being told no. The tests I want they can't order as they are apparently too specialist for general practice and the drugs to find the issue via treatment are too far too off label for them to justify despite studies and clinical efficicacy from other countries. I just view that as a refusal to diagnose and treat me, no point putting it on me if you aren't then going to let me treat myself.
It is frankly absurd to put this onto the patient. It is all about their perceived Physchological basis of the disease, they will humour you on tests and some low harm drugs until you run out of stuff and hope you will finally see the light that CBT will help you.
If there is any test you should get is is a serum amino acid test.
I have done much of the foot work on ME/CFS. Start looking into aldehydes (malondialdehyde specifically) and the role they play. Also, if you can get your genetics from Ancestry it could help you understand yourself more.
And I agree, even when my tests came back weird my primary care doctor would say, "What do you want to do now?"
Argh