Let me start with the fact that this is my first time on a forum. I am hoping to get some input from others going through something similar to myself. Please bare with me...Here's my story

About 9 months ago I was hit head on by a drunk driver. At the time of the accident I was driving and had my left hand on the steering wheel. I braced for impact and when the air bag hit me it pushed my head up and to the right side (away from my left arm). Immediately my left shoulder was in intense pain and felt swollen. I did not go to the hospital because thank god that was the only thing that had happened to me. Unfortunately, that night and on I have been having huge problems with my left arm. My pinky finger and ring finger are numb, I have a hard time making a fist, tying my shoes, typing, doing anything that consists of proper hand function. Also, I have a non stop burning feeling in my arm from my neck down through my left pinky and ring fingers, I can't rest my elbow on anything without numbness and pain. I get twinges of tightness in my pectoral muscle and neck, Headaches in the back of my head....and so on. The symptoms have gotten better but at the 3 month mark that is where things plateaued and haven't changed.

I have been to multiple doctors who all have said it is a brachial plexus injury, but all of my MRIs and nerve tests come back normal. I had an MRI of the Brachial Plexus, my neck, and my elbow for nerve entrapment...all normal. EMG/NCS both normal....Today I read something about TOS and am really hoping this is the problem because this constant pain and discomfort is literally driving me crazy, making me depressed, and has changed my everyday life. My neurologist has injected me 3 times with steriods with minimal results and he has basically given up because he doesn't know why I am not getting better....he is now sending me to physical therapy which I start on Friday.....

My questions...
Could this be TOS?
If this is a Brachial Plexus injury is it normal to still be in so much pain?
Is this going to be permanent?
How can I get a definitive answer of what is going on?

One thing is certain...there is nerve damage or compression of some kind....

Any input will be much appreciated! Please help..