What Causes Recurring Headaches?

I get recurring headaches right above my right eye, and the pain shoots through the side of my right side of my head down to the right side of my neck. Usually they're bad enough to make me nauseous and are so debilitating that I have trouble doing anything. They last for about 24 hours (start later in the day, and itll carry over into the night and I'll wake up with it) .I drink about 10 glasses of water a day, exercise moderately every day and eat healthily, yet these headaches happen about once a week. Excedrine/Advil/Aspirin ect help with my milder headaches, but not these. Any ideas what these are?