It could be if you only get it after a long session that you are just getting a bit dehydrated. Bring a glass of water with you to bed and drink some during the sex session. You can loose a lot of water sweating, spit and I guess though the love juice you produce. Give it a try if it makes no difference at least then you can rule it out as a reason for the headaches.
Guess drinking water or a glucose drink half way thru would help but I wouldn't reccomend you drinking loads of water before hane .... well not unless your into watersports .................... :shock: lol
Try having a drink between partners ( call it a mid session interval lol )
Davie ( who would love to be in the position to get headaches after sex.... still where's there's life there's hope lol )
da fugly one returns lol :P
try taking your curlers out before you lie down :-)