Sounds like classic primary care rhetoric. 'Let's try this' as if he is throwing darts at a board. I doubt a neck MRI will show anything. The subtle neck issues are rarely imageable. At the low dose commonly used for PCS related headaches, amitriptyline is usually not a problem. But, I don't think it is an answer, just another dart to throw.

Do you have access to a Physical Therapist who has gentle upper neck skills. Not the 'let's work on range of motion' type but rather one who can use some gentle traction and manual mobilization to see if you neck will settle down?