I've had a really similar experiance. Sex was a big trigger for brain-pain haha. I'm not sure why but it passed after like a week or so.
Is it one of those head-aches when you feel almost like feverish, or lethargic when it comes on and every time you move your neck/head the pain just kind of simmers your brainz?
http://www.drdaveanddee.com/headache.html