Ok so the back of my head hurts a lot when I begin to masterbath. It's a painful experience but when I stop, it starts to decelerate. I am 17 years old & wondering if this is serious. To add on, this happened two days ago when I was doing that but earlier that day I was exercising (running, weight lifting & boxing) and it started to hurt. It especially hurt when I was boxing as when I hit the punching bag, my head hurt with ever hit (this was intense exercise). So I was wondering if this was because of the exercise or of masterbathing (I do do it often). Thank you.