I stopped getting headaches after stopping paracetamol. I have not had a headache in... Years, apart from when I have head colds. Best cure, apart from sex, bananas as they are laced with lost of simple sugars your brain loves... If your a smoker, then it is possibly too much smoking cigarettes, that is one of the hall mark signs of CO poisoning. Sleep is also good.
Have you ever used a firearm? if so what was it?