I agree with bridgeback2 .

Am sure this is stressful trying to figure this out.
It will be a rule-out process, especially neuro as it is so very complex.
Keep going. The answer WILL come, so don't give up.

You did not state your age, any other existing conditions (diabetes?) you may have, your height and weight, what meds you are on or have tried. Am an RN and know those things are part of a bigger picture when ruling out a diagnosis.

Yes: by all means bring up small fiber neuropathy and insist on a biopsy from your neurologist. If he/she says "No" find one who says yes.

Doctors are also imperfect humans: fallible, and a good near will do what a patient asks, if the request will help them find answers for you both.

Good luck and keep us posted.