6 months too soon?

My boyfriend and I just recently went to his best friends wedding, we've talked about marriage before and how we both know in our hearts that we are the one for eachother, now all of a sudden, he's saying he doesn't know anymore, I know he's not cheating or anything like that, but just don't understand. He's 24 and im 21, yes we have our whole lives to date and blah blah blah, but idk what to say or do about it. I've tried confronting him and asking him but he just says idk or says because of my past (I've been married before but he cheated, we never loved each other, we just got married because it was expected of us by his family) he doesn't know of he wants to because he doesn't know if I'll change my mind but I tell him everyday how much he means to me and how much I love him. But he's still hesitant.