Headache after sex? and it lasts for too long and I need to take a pill

I am age of 35+/Male. After having sex with my GF or Masterbate. Often i get headache within few hours or next day.

Headache stay very long time until i take pills. 

Is it me only that happens or is it also with many. How do you fix this problem? I am thinking to stop sex and get divorce or get seperated with my GF, its making me uncomfortable and i do not want to make my GF life screwed for my personal issues.

Can anyone please help me?