Have you had an evaluation by an upper cervical chiropractor?
A spine specific phys therapist may be helpful.

If it is mainly neck pain bothering you now, and xray/MRI show no issues in the c spine & neck it probably is soft tissue injury.

But if c spine is misaligned that can cause ongoing circle of discomfort.
It does take time for soft tissue to heal, but therapies can be helpful.

Like ultrasound, low level laser or LED light therapy, heating pad or cold if that helps, massage , as well as maintaining good upper body postures.

The head can weigh 8+ lbs, so be sure it is balanced on the spine and not forward of the body.