I thought that I had ON after doing internet research, but later found that it was just tight back muscles pulling the scalp and neck tight. My pain doctor made the diagnosis.
Awful headaches-neck, scalp, eyes, shoulders-that nothing would stop. Rest was the only thing that helped,
Try remedial (or sports) massage and you should soon know if it is muscular as the masseuse will be able to see what condition your muscles are in, and after being treated the pain should go.
Continue with massage on a regular basis-every 2 or 3 weeks at least, to get on top of it.
Muscles have a memory and need to be retrained!
Try taking magnesium to remedy a magnesium deficiency which, as in my case, can cause of my muscles spasms and tightness.
Magnesium was the 'miracle cure' for me. So easy and fast acting. Expect results in a week or two, and continual improvement as long as you keep on it.
Research it on line. I take magnesium chloride in water.