Since your MRI isn't very conclusive, and now that I read more of your symptoms described.. I'd like to suggest you read on our thoracic outlet syndrome forum..TOS for short.. See if it applies after reading thru the sticky threads..
There are sticky threads for Drs, PT & Trigger points too along with the main TOS info sticky thread.

It can occur after a whiplash type injury, along with poor upper body posture, and work /activities can be a factor also. It is not well known, and somewhat controversial, so your dr may not even consider something like TOS.
By any chance do you also have a repetitive, or desk job?

I suggest starting with the first post here , it is a crash course on TOS and has therapies linked too.
Our Useful Links - Websites, Articles & Polls -
http://neurotalk.psychcentral.com/thread84.html

The main TOS forum page link-
http://neurotalk.psychcentral.com/forum24.html