I agree with Londres70 that if you have not seen a Neurologist yet, and are able to to do so, make an appointment. I have a couple of thoughts of this;
1. you may have a pinched nerve in your neck that could be causing the pain. An x-ray will not always show this, thus the need to see a Neurologist (be sure to have all of your files and x-ray sent to their office before your visit).
2. You could have a tear of the rotator cuff or deltoid muscles/tendons which will not show up on an x-ray.
Either way, you will probably need an MRI to confirm or rule out these injuries.
I wish you the best.
Well i'll tell you from experience. I had an accident with my arm once and it turned out i had nerve damage. That will not show up in X-rays. Nerve pain generally feels like a harsh internal burning that shoots up the arm or wherever the nerve is located.
Have you seen a Neurologist at all?