You need to be evaluated for autonomic neuropathy...a subset of SFN. It can effect your heart rate, BP, breathing, etc. There are several autonomic tests that can be done to include, holter, 24 hour BP, tilt table, QSART, etc. A cardiologist or neurologist can order these tests and there are medications to help with certain aspects of autonomic neuropathy. Cardiac vasospasms may cause chest pain like you describe and is an autonomic dysfunction (a treatable condition).