While not diagnosed specifically with ON, my head pain was certainly in that area-let's say 25+ years! Plus sore neck, shoulders and lower back.
Brought on by work stress and too much computer usage with poor posture. So self inflicted. The things we do for money.
Retired for 5 years, but it is only in the last few years that I've found relief.

The first instance followed a suggestion from my pain Dr. to get remedial massage. BINGO!
My back muscles were knotted, pulling on my neck muscles, leading to the headaches. Not a cure but a treatment. Worked immediately, but needed fortnightly treatment.

The second thing was magnesium oil. I drink it in water. Within a week or 2 the muscle tightness had gone, and I no longer needed the frequent massages. So a cure. Been on it for 8 months. Everyone else I've suggested it to loves it as well.

The third thing I now do for pain is to take a large dose, say 2 teaspoonfuls, of Vitamin C powder every day. In water, with a bit of bi-carb soda. Been on this about 2 months.
My overall pain levels have dropped dramatically as a result of the magnesium oil and Vit C.

I have stopped taking Celebrex over long-term-use concerns, with no disadvantages.
I have stopped taking Tramadol. I was at the max dose most days, and waiting for the next dose.

All I take now is paracetamol, but not at full daily dose.

Considering the pain I have been in and the diagnosis of having a worn out neck, this is quite a remarkable achievement.
I am so pleased to be off those drugs too. To get off the Tramadol only a few days of restless legs, sneezing, nervy feeling. So I was becoming addicted, I think. Glad to be off it.

I would strongly recommend these treatments to others with chronic pain-you may be as successful (and surprised) as I have been.
Interestingly, none of these successful treatments came from the medical people!

I'm also wondering if the Tramadol was actually causing some of my pain. I've just been so much better without it.
Food for thought.
Yum!