I get these type of headaches with the change in weather - any barometric pressure change will send me reeling. With the spring weather fluctuations (here we've been going from warm and sunny to snow in the span of a couple of days), and the fact that you are starting to ride outdoors more often, could that be the cause?

Could also be as others have said - allergies. Things here are just starting to bloom, and I KNOW that over the next few weeks not only will I have headaches, I will also be reaching for my inhaler.

SheFly