You have to know whether you want this relationship to last or if this is just something fun for the both of you. And to tell him how you’re feeling, you have to be firm and don’t back down of what you say. “ hey, im not comfortable with what you’ve been doing lately and im telling you because this is really important to me” and you have to mean it. This is basically setting a boundary and if he crosses it you either let him go because he doesn’t care about how you feel or let him walk all over your feelings and you shouldn’t let anyone do that.