Personally, I think it's your girlfriend's job to tell him something. All you're doing is fueling him even more. This guy is very calculating and sorry to say but I think the age difference makes a big deal here. I'm sure he knows you're alot younger than he is and he might know how to push your buttons a little. Don't prove him right! Your girlfriend needs to tell him to stop. If he hears it from her then he'll probably stop. If she refuses to tell him, then you better think twice about the relationship you're in. Just my 2 cents.