Welcome to NeuroTalk:

I would suggest to limit the heating pad. Instead do an ice pack twice a day, for about 20 min.

Use heat only for a maximum of 10 minutes. Heat makes nerves
fire more and makes pain worse in the long run. And your location is a prime shingles spot. If you have had chicken pox as a child you could be activating the Zoster in
the nerve roots there.

Do the ice for a few days, and see if anything changes.

Another option is Salonpas. They have a new large stronger patch that comes 5 in a box, for a little less than $10 at WalMart. One patch is quite strong and if you have inflammation there a patch may work. It will tell you if you have inflammation or referred pain. That area may be referred from parts of the heart, or gall bladder.
This is what the box looks like:
http://www.walmart.com/ip/16935761?w...l5=pla&veh=sem
These are the new stronger improved ones approved for pain by the
FDA...a rare thing for OTC products.

I've had great success and relief from Salonpas over the past years.
They really do work for some types of inflammatory pain.