Well I did the same thing, I had to sit down with him and point out that I was open to his doing these things but that it would take time before I would be ready (if ever) to do this myself. He was cool about that, and I would once and a while put on a diaper for him before bed. I just had to get used to the idea of myself doing it. You have to know that I personally have no fetish, and did not know about this community before I meet DF.
Though another thing you are going to have to sit down with him about is that while you may some day wear and even have fun in is this world, you do not share the fetish. This is to say that he can not forget about your needs in the relationship when it comes to both emotional and physical. This is the part that I have the most trouble with because if you do not make these things clear you may start to question if it is you or the diaper that he likes. Right now you know it is you because you are not in the object, just make sure to draw the line in the sand as to be you meet.