This is my opinion on your post. If you tell him he might want to call it quits. Yet by not telling him, it is not giving him a choice. Reverse the roles and see what you come up with, and his opinion can still differ from yours, Relationships lasts a lot longer if they start as friendships. I personally probably would have a hard time dealing with if were you telling me, but I would feel better about it if I knew that the relationship would be exclusive as of now. And for it coming back thrown in your face, when ppl fight they say hurtful things. They want you to feel their pain. Now you are in the beginning of a relationship, when the newness wears off it will get harder to tell him. And also don't you want to be able to overcome any difficult challenge or struggle life brings you both? Good luck with whatever you decide.