You sound exactly like I sounded 10 years ago. I met my husband 10 years ago and we have only been married for 4 years. He too did not want to get married and knew how I felt about it, but our reasons for getting married were not what it should have been, not for love or anything like that...
I can honestly say that it was the biggest mistake I ever made, my dreams of the beautiful white wedding, the ring, the white picket fence, the kids(I have and I adore them), the dog etc etc have all been a fantasy, it is just a dream and in reality marriage is not about that at all. Firstly, if he doesn't want to get married and he feels trapped into doing so he will despise you later. Secondly, a marriage takes alot of work and commitment and once you are in it, it is a drama to get out. Not too scare you or anything, but I wish I never got married...
Maybe I am pessimistic because of my bad experience, but it has made me realise that life and especially happiness is hard to come by and if you have that with him treasure it and try not too worry about the what if!
Hope this helps