postconcussion,

Your admission that you cannot turn your head quickly or stretch it without pain is good evidence of an ongoing neck injury. I suggest you search for a Physical Therapist who has a good reputation for working with upper neck injuries. A physiatrist or rehab specialist is also an option. An orthopedic neuro-surgeon is a bold move be may have the diagnostic skills you need. Avoid any discussion of surgery until you have exhausted all other options. Some neuro-surgeons like to cut. There are also some who are well experienced with a wide variety of treatments.

A multi-discipline spine clinic might be helpful. They may have PT's, neuro-surgeons, chiros, pain specialists, acupuncture, etc.

Getting help with a neck injury or even just a diagnosis helps to direct you to also focus on neck position and related issues. It is amazing how a injured neck can magnify PCS symptoms.

My best to you.