I know it’s very frustrating.
Been thru so much testing and prodding over the years with no help from any of 6 neurologists I went to.
All I was told is that I’m very unique and sorry we can’t help you!
Going to start a new infusion this month called Retuximab, for many things including CIDP.
It’s a monoclonal antibody.
IVIG infusions did not work for me in the past.

@walk4life Please read up on the cortisol test, I understand that the blood draw needs to be done early in the morning. My endocrinologist looked at the time of day on the blood draw for me I literally just made it under the wire. My PCP had ordered it and apparently did not know time of draw was critical and neither did the lab doing the draw. I live in the Dallas area and these are doctors and labs of major health providers, so not a small town by any means. Thankfully my endocrinologist knew to check.
Also, have you had your Sed Rate tested? https://www.mayoclinic.org/tests-procedures/sed-rate/about/pac-20384797
Sed Rate and CRP are the two inflammatory tests. They are both non-specific and do not directly lead to a Dx they simply tell doctors about inflammation in your body. Your rheumy should be able to identify/eliminate an autoimmune problem.