Eliora, I would see a chiropractor. You might make sure they use the Palmer method; I think it is the best. And they do the most thorough manual exam. They are much less expensive than neurologists and orthopedists. And you can usually get in to see one same day, at least same week, without a referral unless your insurance requires one. I see chiropractors often and get great and immediate relief. Some people are afraid of the adjustment, but even if you don't accept the treatment, you know more about your situation after the consultation. Sometime the shift in the spine is so small that it isn't apparent on an MRI and wouldn't be anyway when you are free of the weight of our heavy heads while lying down.
I hope you have luck.
You could ask for a CT of the neck and shoulders which would give you more information about soft tissue than an MRI would.