Omg help. This is so annoying

So I literally just finished masterbating. But when ever I do it I go to squirt and if I stop my self from squirting cuz I want to go on longer moments later I start spazzing out and shaking and I can no keep going. Even moments after I stop doing it I am still tense and shake a little and have to lay there for a moment to catch my breathe. Does this happen to anyone else? I am 15 if that helps. And can you go further then that. If so how do you when you can’t move??