A Question of Understanding Need?

"I'm scared to tell my fiance about how much of a sub i can be. My need to satisfy him in and out of the bedroom goes beyond any normal relationship. He knows that I have been in DOM/SUB relationships before but he isn't really in to that kind of thing. I just cant get him to understand that all I want to do is make him happy and proud. If I do something wrong then punish me.I always ask him if im allowed to do this or that and I also make sure that his needs are met but he is still holding back. It irritates me so much because I really need that control over me and he just wont do it. How do I get him to understand my need of being a sub without scaring him off?"

First, I would just like to say that if communications was a class I had to take, it would have ruined my GPA.

Why do I always seem to have questions as soon as I sit down to answer questions like this? First question that comes to mind, is why so scared to tell him?
I understand being nervous, and having a terrible time sharing some thoughts, but I'm not sure about the reasoning for being so terrified of it in this case...?

In my humble opinion, the best first step would be to come to an understanding of whether you need, or want his control.
Do you need to have it in order to stay with this man forever? Do you want it and can live without that control if it becomes an either/or situation--him or D/s.
And, if all you want to do is to make him happy and proud, can you accept that doing so might take the form of not being his submissive? Because it is quite possible that D/s is something he won't ever be "in to".

You have obviously made it to the point in your relationship where a commitment has been made, but this sounds like something you need to resolve before taking the next step. It seems to me that a man might feel terribly misled to only find out something like this after the wedding.
Telling him how much of a sub you are shouldn't be able to break the relationship, and if it does, then was the relationship solid enough to last in the first place?

I think that once you have clearly established what is need and what is want, it would be well worth your time to sit down and ask him why he's holding back. Then talk to him about how important D/s is to you.
You entered into the relationship with the understanding that it wasn't based on power exchange, and you agreed to an engagement with the same understanding. So chances are, this might be somewhat of a confusing turn for him. 

You say that you want him to punish you for the things you do wrong. It is possible that you might be able to incorporate D/s into your relationship, but that punishment will not be a part of it if punishment is something that he can't be comfortable with.

To put it mildly, communication isn't my strong point, and phrasing things in a way that doesn't scare people off is a skill that I still have no grasp of.
But I do think that approaching him in a manner that doesn't judge his refusal to Dominate is a good step in order to avoid him judging your desire to submit.

My brain hasn't been functioning at peak performance this week, but I hope that you find something helpful here, and I wish you the very best of luck. And please do feel free to continue the discussion in the comments--I don't think that I have ever answered a question without leaving something out lol.