Here is the issue with your test. They are testing your large fiber nerves. The large fiber nerve test in most cases will come up negative for any issues. The large fiber test can't detect small fiber nerve issues. To get the correct test for the small fiber nerves you must get a biopsy of the skin from a specialist who is knowledgeable about small fiber neuropathy. I have a very serious case of SFN and it took 20 years for a diagnosis through a skin biopsy. They all thought I was crazy. With the pain I was getting I knew I wasn't crazy. With mine I get a devastating itch, burn, stabbing, electric needle stabs all over my body. The itching part is one of the worst parts. My symptoms come about emotionally, physically, mentally, by the heat, by the sun, during the winter times, after hot showers eating spicey foods, eating sweets, exercising, sleeping and dreaming, working, and alcohol consumption. I too felt as if life was hopeless but I still fight on. I take many meds and am still trying to find the cause of my issues. I know more about SFN than most of the Dr's I see which is very frustrating. Just don't give up, question every weird blood result and don't allow anyone to make you feel as if you are crazy and finally demand a skin biopsy for the test. See a heamotologist a rheumatologist an endocrinologist, dermatologist and of course your neurologist and hopefully you will figure things out.

Best of wishes