I think I agree with other posters that 'Am I your girlfriend' sounds a bit 'off'-it sounds a bit high-schoolish, to my ears. That's just my feeling though, I could be way off base. As far as the conversation goes, I am always fan of being direct, and open-games are not of any use in this sort of situation (or really, in any other situation). I would just say something like-'Name, I feel like we're really getting on well, and I feel that I'm at the stage where I would like to consider exclusivity. If you're not ready yet, I'm up for discussing why, and listening. But long term, I am looking for a monogamous relationship, and if we're to continue dating, that's my ultimate goal.' That sounds a bit stilited, I'm afraid-I must confess I've never actually had a conversation like that. I've been with bf for three years now, but we just sort of slid into our relationship, with no awkward conversations. I do agree with the PP who said if it's the right relationship for you, you can't mess it up. Good luck!