If you really feel uncomfortable which I think you are since you're asking this, tell your boyfriend. It isn't being rude if this is making you feel uncomfortable. Sometimes it takes both individuals to come together and compromise, not everyone is similar and that's why you guys have to look into each other's problems. You went once and gave it a shot, but it didn't go the way you liked, at least you tried. Though I'm going to be perfectly honest, the more you do it, the more comfortable you will be, though don't pressure yourself.