Do you also feel kind of lethargic and tired with your headaches? I got that pretty bad earlier in the fall, turned out my blood sugar was going nutso. I wasn't actually eating enough to keep my glucose up, and since the brain thrives on glucose, when it's insufficient it kind of just shuts down. So I agree with (the other) Heather -- maybe look into your glucose levels. A good way to be investigative is to see if your headaches occur at any particular time of day, or after eating any particular kind of food. Mine would always happen almost at 3:30 exactly, it was weird. Anyway, let us know what happens!
