For the past 3 or 4 workouts I've been doing I've been getting headahes about halfway through that usually last up to an hour after the workout is done. I've also started getting very mild headaches before races that usually go away when the races start. I'm well hydrated (1.5 liters of water during the day of the workout +.5 liters of Gatorade) and my diet is what it's been for 3 years (I'm in high school so this consists of oatmeal and tea for breakfast, a bannana and yogurt for a snack,and a peanut-butter and honey sandwich for lunch). Any thoughts on why this may be happening and how I could stop it?