I've had a headache every day for the last fortnight, it's not constant, but every afternoon or evening, there it is again. It's not migraine level, but intense enough to be wearing.
My initial thought was it was part of my cold, which seemed to be staging a last stand in my sinuses, but I'm not really getting a lot of other cold symptoms anymore, so I've started thinking that may not necessarily be the case.
An obvious possibility is my new glasses - I switched to varifocals just under a month ago, or a combination of new glasses plus posture - the varifocals are inevitably going to change my ergonomics when I'm reading in a reclined position, particularly precise head/neck posture. The third option would be something otherwise c-spine-ish. I'm not aware of having done anything to my neck, but I've a history of neck issues suddenly popping up without warning, and sleeping with a collar on the other night seemed to help a little, but not enough to be entirely sure.
So I'm going to have to spend a few days experimenting with different combinations of things to see if they make a difference, starting with going back to my old glasses for a day or two.
Bah, this is a headache....