Have you had your eyes tested? I had constant headaches for a few weeks, which started only a short time after an eye test. The headaches symptoms didn't seem to tie in with eye strain, so both the doctor and I dismissed this as a cause. I took a lot of pain killers, following the doctor's advice, to no avail. Then in desperation had my eyes tested again. Lo and behold there had been a significant change for some reason. New glasses (expensive ) and problem solved.