Why does it hurt my penis if i musterbated for about 4 time?

What are you doing to it that makes it hurt? You should be able to do it until your arm hurts without a problem.

When I was 19 I had a gf I normally saw only on Sunday for a year and a half. She used to make a game out of seeing how many times she could make me come when we were together. Usually about 8 or 10 times for the day but the max was 12. She never hurt it and it was never sore the next day. Whenever we were together she had her hand in my pants as soon as she got in the car and I loved every minute of it