what I think may be happening is that you are holding your breath during love making. Try breathing steadily and make sure you are taking long breaths in as well as panting when you are excited. This might really help the headache situation.
As for orgasms, it seems like you used to have them-what has changed in the interm? In the meanwhile, why don't you buy a vibrator, if you haven't got one, and try having your boyfriend stimulate you with that. Start out with a little vibration not directly on the clitoris and see if that is stimulating enough. If not, try it more directly on the clitoris but not so much that it starts to get numb. Make sure the whole area is slick with some kind of lubricant ( get one that isnt sticky like Eros, of FDS etc) and also try stroking the clitoral area with a finger - and perhaps another finger inside of you or a dildo inside. Play with speed and pressure and just enjoy yourself. Let me know if one of these gets you over the top!
I read something about this before. There are two types of sex headaches: the first one is relatively harmless. To my understanding, there isn't a cure... they just recommend taking 2 aspirin or Tylenol before sexual intercourse. These headaches occur before or during orgasm and are thought to result from muscle contraction, and/or blood vessel dilation.
However, the second type of headache is more serious. It is rare, but it happens. It is a brain hemorrhage. Although it is rare, you should see your physician just in case... and then you can relax after that and hopefully the aspirin will help with your headaches.