SO is super vanilla, I love anything but vanilla

we've been together for 10 months now and my SO is completely vanilla in bed. When I told him that I wanted more like of the like ass slapping/hair pulling kind of sex, he tried and at first it was fun to just see him try to please me in that way, but I just want to have like the aggression there without me having to tell him what to do. On the other hand I also don't want to make him uncomfortable with it and push him into doing something for me that he doesn't want to, how do I explain this to him? what do I do? I'm 19 btw and he is 20