So i started having this pain in the back of my head/neck about two days ago. I was lying down in my bed late at night, masturbating, and then when i finished the pain started to go on for about 10 minutes, then stopped, i tried massaging it and it helped. Yesterday, it happened before I even finished, during the whole process. So currently i'm afraid to masturbate becouse of this thing. Is it a serious matter, or something that goes away over time? If not what doctor i should contact? Thank you. If it's not enough information, I can add.