It could still be your neck even without definitive proof. I have a similar situation with my lumbar spine. I'd definitely continue with PT. If you're not happy with your PT you can try another.

I'd check out carpal tunnel.
Are you or were you on any prescription drugs? Antibiotics?

Suggestions:
Give up sugar and alcohol at least for now. Probably change your diet although I don't know what you eat. There are a number of posts from members about diet and PN and what has helped.
Start keeping a journal to try and get a handle on your triggers.

Hope this helps.
Pinkynose