Missa,
Don't despair, many of us had the same thing happen. I know it's disappointing when a Dr leaves you hanging- at least you know this dr isn't the one to dig for answers for you.
I would use this time to seek out a more knowledgeable Dr.

If PT isn't hurting you or making anything worse I think keep going for now. But if anything at PT makes you hurt more or the symptoms get worse stop right away. Do they seem to be helping you at all?
step 1 should be reducing your pain -with ultrasound, heat, massage, trigger point

hopefully they are working on your upper back, neck, shoulders arms and wrists and talking about posture and showing you how to be more aware of that.
There are plenty of things that can be tried - second or even 3rd opinions - but that goes back to finding a good and caring Dr.

OR-
If you think it might be work related - have some consults with a few wc attys { they are free}- check them out/ interview them and get as much info as you can before signing , if you decide to do that route.

Most standard tests will come out normal- that is the tricky thing with TOS- why it's difficult to prove.
some will have multiple "crush" that means the nerve is pinched/affected at more than one place - so those tend to show up on EMG/NCV