I've had these in spells on and off for years. My known causes are:
Pregnancy - all done there, no more ta!
Combined contraceptive pill - stopped it and the headaches stopped but then came back...
I cut out caffeine despite only having one coffee a day and the headaches stopped for around 3 months.
But they're now back. What else can I essentially cut out?
I drink plenty of water, no alcohol, walk every day, sleep well and plenty.