I've been seeing this guy for a short while, and we had sex for the first time on Friday. Luckily, he had condoms with him, but asked me first if I did, which I didn't (I wasn't planning on this happening) but now I'm thinking- how stupid is it for me to not be prepared. But, what size do I buy? I guess he's average. I know girls have condoms for "just in case" but how the heck do you pick them out?