How to cum with a vibrator

Ok I've never actually had an orgasm and I've been with my guy for a year and a half. I got my first vibrator through a friend the other day. And I find its good but I get to a point where I have to pee and the feeling then vanishes like thin air. I don't end with shakeing knees nothing. Idk if I'm doing it wrong or what. Any advice would be appreciated.