I had a similar problem. Whenever I would do an intense workout, especially a long or fast run I would get terrible headaches that would last the rest of the day. I talked to my doctor and she told me that there are three common causes for this kind of headache. Drinking caffeine at any point in the day before a workout, not getting enough water during the day or during a workout, and not having eaten recently enough. Cut out the caffeine, drink a lot, and eat a snack 30 mins before workout.
Submitted by lion_girl130