There are several different methods of testing for neuropathy and it's possible causes, but everyone is different. Some of us never get a real diagnosis because the cause can't always be determined.
It took 3 neurologists and 2 neurosurgeons over 10 years to tell me that I have idiopathic poly neuropathy in my feet. In other words, they can't determine it's cause because I'm not diabetic, and they've done every test out there, sometimes more than once, and the results were "normal".
So I've been told to just "deal with it", and to treat the pain as best I can. I'm already taking 3600 mg of gabapentin every day to dull the pain, but doing something like walking gets harder all the time.
I'm not ever going to get better, or have less pain. I also suffer from osteoarthritis in my hips, knees, neck, lower back, and right elbow, so my quality of life isn't the greatest.
Get a referral to see a neurologist and get the tests done , you might be lucky and get a straight forward diagnosis and a possible treatment option.