I also have to agree with Di and Jo Both...
Your Dr should be suggesting some other types of interventions such as PT. It sounds as if you may need a Physical therapist that is trained in TOS to work on those muscles to get them to loosen up for you a bit.
It seems all he wants to do is injections and then send you on your way. As Di said giving injections under the arm can be very dangerous. If I were you I would ask your lawyer if they had a neuro they could refer you to that specializes in TOS. Di gave you a good recommendation it may be possible that your attorney can get him approved to be your primary. A good TOS Dr is always in your favor and one never knows if they may need surgery down the road and if this happens you will need a specialized TOS surgion.
Try to do the stretches that Jo has told you about and don't lift anything heavy!!! Weights are a NO, NO....
Take care and I do hope that this starts to smooth out for you a bit... We have all been there and some are still going thru it... It is a very difficult road ahead and unfortunately it is one way... The bumps should smooth out down the road though...

Many Gentle Hugs
Dawn