okay, my boyfriend and i have been really good about not having sex without some form of protection, and we've only had sex three times. but we tried to use a condom the other day, and it would not stay on. we tried three before finally giving up because neither of us really wanted to do it anymore. is there something we missed while trying to put it on? is there any particular reason it won't stay? i've told him we can't have sex without something to prevent pregnancy, so we haven't, but i need to know what we're doing wrong. it's completely frustrating that we can't figure it out.