Ask HN: What should you do if you think you might have a rare medical disorder?

Context: have seen PCP, multiple specialists, taken a lot of blood tests, and have done considerable research, without receiving a concrete diagnosis (in the US). Chances are I'm experiencing some undetectable auto-immune or poorly understood condition (like CFS). I've become incredibly frustrated and I'm curious if anyone here has ever found themselves in a similar situation and figured out a reasonable strategy to navigate the medical system. Should I be considering Mayo Clinic? Is there any online platform where I can poll a lot of specialists all at once? Other options worth considering?