Welcome to the Pain Management Forum. I am sorry to hear about your continuing pain.
Have you had an MRI of your spine? I would want to rule out possible spinal structure issues as a pain causation.
I don't think you would be out of line to request an EKG of your cardiac activity. This would also help you put to rest heart problems. Once those two tests are completed and negative you will have less possibilities to consider. Than I would get myself to a good diagnostic physician associated with a teaching hospital. Be assertive and ask for answers.
I wish I had exact answers for you. I am sorry that your search must be one of elimination. I do wish you the best and hope that you will keep in touch with us.
Best of Luck to You,