I don't get nervous before my spars anymore, so I know it's not that. I know I'm not dehydrated because I drink quite a bit of water, and I'm sure I'm not out of shape. My headache that I had from yesterdays spar is gone now. The thing is, I dont get hit A LOT when I spar. Yesterday, I probably only got hit with 3-4 good shots, with all the other shots felling pretty light. And it was only 3 rounds. I didnt get a headache until about an hour after the spar. Ive tried to look up info on this online, but couldnt find any thing. Thanks for you guys reply, and I'll probably end up talking with my coach or a doctor about this.