What sort of things do you say?
No guy likes to be insulted or hurt, and guys, as well as girls, have different tolerance levels for such things. Find the time to talk to the guy you like and explain to him why you say/do these things. Chances are he'll understand and the relationship will be better because of it. Honesty is the best thing for a relationship, communication is the key. Just keep in mind, just because you told him why you do it doesn't mean that he'll be able to take it forever.
what to do