As Dr. O says, you should definitely see an opthalmologist. And while you're waiting for your appointment, check out migraines:
http://adam.about.net/reports/Migraine-headaches.htm
Note: Do not try to self-diagnose, but definitely ask questions of the doctor when you see him.
There are many causes from glasses to things more serious. You should see an ophthalmologist.
Dr. O.