Why wont this go away?!!!!?

I have had a none stop headache for about a week now, and its driving me frickin' crazy!!!! Ive taken just about anything for it, and it still does not go away. I don't know if its stress, or im not getting enough sleep, or that I haven't been eating much, I have no idea, but I need some sort of advice, I am starting to think its something much worse then those ideas, because I have had thyroid cancer, and I am wondering, if it could have spread to there :( Its worrying me lots!!!