Hi Jim,
Sorry to hear about the pain you have in your arm, I'm also having similar issues, which now has turned into a "frozen shoulder" because it was just being ignored, you should take this seriously and see your GP and ask to be put onto either Gabapentine or Pregabalin theses medication have specifically to deal with nerve problems and issues that normally start in the arms or feet, legs upwards so as soon as you feel severe pain, that a normal pain relief does not control, that it when you need your GP to prescribe medication that is nerve related.
Hope this was helpful, do take care.
Good Luck !!