It depends on his values. Most people, from what I have seen, don't want to wait until marriage anymore which is probably because society is totally different than what it was in the past. He will either; decide to respect your decision and stay with you, try to pressure you into sex (which would be horrible), leave you but respect that you want to wait or he will not understand it and leave you. Nobody on this website can predict what your boyfriend will do (or whether or not you will change your mind for that matter) as we don't know you or him on a personal level. My advice would be to tell him yourself and if you are nervous- plan how you will say it before hand. If he wont accept waiting until marriage with you and tries to persuade you to do something you don't want to do then the best option would be to leave him. But I would hope that he would want to stay with you and wait until marriage. I hope that he either will wait for you or you will find someone else who would be willing to wait until marriage. I am also considering waiting until marriage too so I can see how it can be hard to find a guy who would be willing to wait.
I wish you the best! :)
