Masturbation headaches

I masturbated about 5 days ago and I caught had this immediate painful sensation in the back of my neck and an painful headache as I was reaching climax . This has never happened to me before . The next day or two later I masturbate again to see if it was a fluke or something and the same thing happened again even more painful in my head . Since I’ve had a headache for 3 going on 4 days . I took pain killers and they have almost no effect . I read it could be because high blood pressure but I don’t have that . What could it be or how serious is it ?