Have you ever had any really good soft tissue / hands on therapy for your neck?
Not stretching or strengthing... Massage, ultrasound, Interferential stimulation, manual trigger point etc .
Depending on what and how your previous concussion hits happened, your neck could have been strained. Whiplash, side hits that knocked the head and neck sideways?

The headaches and pain could be from trigger points in your neck and upper back muscles
Neck pain and headaches sound more neck muscle related to me .
Many sites online about trigger points and even symptom matching and locations.

A very good PT can often do a much more complete assessment than most drs will do .
If you are on computers or other devices for work or school, the head forward position is very strenuous on the neck muscles esp if they are strained already..