Recently I've learned that half of the people are slow caffein metabolizers. The caffein stays longer in their system and it might negatively affect their sleep. Considering how many people drink coffee, I think a lot of people are affected by this.
A genome sequence shows I'm a slow metaboliser (I expect more will show up with more research).
I feel terrific now.
I need to cap at 2 espressos per day before noon at most, or I start suffering side effects like poor sleep quality. People really need to reframe their coffee consumption from food to drug and understand their own usage and effects of said drug.
I strongly recommend Barleycup as an alternative morning cuppa.
Alternatively, you might be prone to migraines, and thus are sensitive to headaches of all kinds. That's me, I truly hope that's not you (wouldn't wish that upon anyone).
The headaches are reliably cured within maybe 20-40 minutes by application of more caffeine, so I don't think they are migraines.