When masturbating, the pleasure abruptly stops. why?

During masturbation, I often find myself experiencing pleasure, but then it abruptly stops. I reach a climax but it doesn’t feel like anything that strong? I don’t know how to describe it. It's as if the pleasure has a time limit and goes away after a few seconds. I use my fingers to rub the top bit (not sure what it’s called).

Is this normal? I want to experience an orgasm so bad but I’m never quite there.

Is it possible to have an orgasm without a toy? And how do I do that?