Well, to my mind the first step is to find out why he doesn't want you involved, and what he means by you moving too slow. It might take a bit of doing, but as in every other part of a relationship, communicating effectively with one another is key here. If the two of you can't have that conversation without things getting emotional, write each other letters or emails about it instead - I've always found letters to be very effective in talking things out in an otherwise too emotional situation, not just with partners, but with family as well.
Anyway, sorry I can't help with more than generic advice, but I really think it's important that you both know the why and what before you do anything else.
Mina.