I NEED HELP

So I need help. I'm so confuse.

I haven't have sex, so I still a virgin but I usually masturbate and I don't have idea of how to react. What I mean is that I don't know how to react when I'm in getting to the orgasm. I usually stop because I don't know if it is pee or part of the orgasm so I just stopped.

Any advice?

Also, I'm 17, just in case