If this is an issue of what other guys are saying (im thinking in showers after sport etc) then thats what men are like, they pick on the easiest person, if it wasn't you it'd be somebody else, if they are really nasty punch them and they won't say stuff much longer, I don't believe the view that "Ignore them and they'll get bored" it's a load of crap!
If it's an issue of you being low in self esteem, thinking that when you get intimate with someone they'll laugh or or something, don't worry about that until it happens, and if it does you'll know that they weren't you're time because they are really not a very nice person!