Orgasm help!

I'm 18 and have been having sex for almost 7 months (with my boyfriend of  over a year). He was my first time and the only person I've ever done anything with. Anyways, I want to know how to orgasm. I've masterbated and I know I get close just by rubbing my clit, but then I just stop myself because I feel like I'm going to pee. I get all shakey and move so I stop. Then I can't touch my clit for a bit because it gets sensitive. I stop my bf as well from touching me. Help!