I agree with ng on this one.
However, if you need a label to validate what you have you need to find out for your own sanity. I am typically shy myself so I would make a joke about it so if he doesn't want the lable you could laugh it off. Or you could blame it on someone else to start the conversation. For example, you could say you were talking to a friend today and she asked how your bf was doing. You said you didn't know because you've never referred to him as your bf. What does he think about that? I don't know, that sounds malipulative, but it gets the discussion open and it takes the heat off of you so you don't have to worry about scaring him off.
Through my relationship now, I don't think we have ever had any labels and have been perfectly happy. I rarely even refer to him as my husband.
Labels aren't that big of a deal. If you are happy with the way things are going, I say just leave them the way they are. I was married before I ever referred to JJ as my boyfriend. We never even really got engaged, so fiance was out of the question. I think it is better that way because it is more of a connection. Well, those are my 2 cents for what it's worth. Good luck!