What Causes Sever Headache During Sex?

I am 36 pretty healthy 5foot 8 inces and eat healthy most the time but every once in a while I'll endulg with sweets and what ever. Then I get a headache similar to a hangover after I eat lots of sweets, I'll take pain medicine and it goes away like a hangover, however when I'm having sex with my wife and right befrore climaxing I'll get a terrible pouding headache almost unbearable.