Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
You have a neuropathic pain (i.e., pain from the nerves). There are 2 types of nerves in our body, large and small. The small nerve endings supply the skin and sweat glands. There are two types of sensory neuropathy: small fiber and large fiber (depending on the size of the nerves affected). With small fiber neuropathies, symptoms include burning or buzzing or other vague symptoms starting in the feet and hands then in some cases spreading to other parts of the body. The EMG/nerve conduction studies (NCS) (tests done to check for neuropathy) will not show an abnormality, and a definitive diagnosis can only be made with a skin biopsy so that the number of nerve endings can literally be counted. There are other tests of the function of small nerves that can be ordered, such as QSART testing which looks at how much sweat the skin makes, since sweating is in a sense of function of these small nerves. There are several causes of small fiber neuropathy, including diabetes, vitamin deficiencies, autoimmune problems
The other type of sensory neuropathy is called a large fiber neuropathy. There are several categories of this type of neuropathy, and there are many many causes. Sensory neuropathies can involve just one nerve or several nerves in the body. The symptoms are sensory loss and if motor nerves are involved, weakness occurs. Some types of sensory neuropathies occur and progress very slowly, others sort of wax and wane (with flare-ups) and some are progressive. One of the most common causes of neuropathy is diabetes, and sometimes only glucose intolerances, or abnormal rises in blood sugar after a glucose load can be the only indication (this is called a oral glucose tolerance test. Other causes include but are not limited to hereditary/genetic causes (such as in a disease called Charcot-Marie-Tooth, in which there is a family history of sensory neuropathy usually from an early age associated with other clinical features such as high-arched feet), autoimmune problems (such as lupus (SLE), Sjogren's, Churg-Strauss (in which asthma also occurs), polyarteritis nodosa, which affects blood vessels), and demyelinating diseases (such as CIDP). Vitamin B12 and B6 deficiency, as well as excess vitamin B6, can also cause neuropathy. Some toxins, such as lead, arsenic, and thalium can cause large fiber sensory neuropathy. Other causes include abnormalities of protein metabolism, as in a type called amyloidosis or monoclonal proteinemia. In many neuropathies, both the sensory and motor nerves (the nerves that supply the muscles) are involved, leading to sensory symptoms as well as weakness.
The diagnosis of large fiber neuropathy is made by findings on a test called EMG/NCS which assess how well the nerve conduct electricity and how well muscles respond. Rarely, in some cases a lumbar puncture provides useful in formation, and very rarely a nerve biopsy is required.
I suggest you follow up with your primary care physician for basic workup. It would be important to distinguish neuropathic pain from vascular pain (aka claudication). If it is felt to be neuropathic, you may benefit from a referral to a neurologist.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.