What Causes Intermittent Headaches?

Hi. My boyfriend has been complaining of a pain at the side of his head, like that of a hangover, as though its connected to his ear. This isnt a constant pain, but rather it comes and goes but he has had it for 2 days now and it hasnt let up. He had been suffering from this for a few years now and did have a scna which showed up nothing. This was done a few years ago.