Do you monitor your blood pressure? It might sound strange but I think rises in blood pressure can trigger headaches. I used to have chronic headaches for years and walk around with 2 Excedrins in my pocket at all times. Then an interesting thing happened:
At a physical about 4 years ago the doc said my blood pressure was a bit too high and put me on a mild daily dose of Lisinipril. After about 2 or 3 months of having my blood pressure back in line I noticed I rarely had headaches anymore! Been free of them for the last 3 years for the most part.
I'll tell you another thing that can trigger headaches is dehydration. Big time! Make sure you are getting enough water.
That's all I have on this. Don't know if that helps or not.