If marriage is a deal breaker for you then i wouldn't wait around - you're both adults and know your own minds. If he doesn't want to marry you that doesn't make him a bad person - he's been married four times, maybe now he's aware that he's just not suited to it? It would be unfair on you if he was going to commit to something he knew deep down wasn't right. I would accept his decision and move on if you decide that your love can't outlast this.