Like right now.
What's odd is that it's changed sides, originally on the left side of my head and face. Now it's on my right.
I have no idea what causes it, or influences it's strength. It's weakly correlated with changes in the seasons, in the weather, and with travelling.
My doctor is stumped, as is a whole array of specialists. I know it's not a tumor or anything like that, I have a whole array of fun MRI images of the inside of my head to prove that.
The process of coming up with this null diagnosis taught me a fancy word: "idiopathic", which is medical latin jargon for "damned if we know".
One theory is that I may be one the luckyest sufferers of a cluster headache. If so, I am humbly grateful, because the nickname for the condition is "suicide headache".
It's nowhere near that bad for me, even right now, but it's really really not pleasant at all.