How do you deal with irrationally feeling insecure in a relationship?

As some of you will already know, I am in a relationship at the moment. Quite a serious relationship at that, as we intend to marry in about 6 months.

My girlfriend is the most amazing person I know. Not only do I deeply love her and care about her, but I have also come to see her as a role model for me.

She really is a nice person. She never judges people, she is kind, honest, very sincere and just generally a better person than me in every way you can imagine.

I have never been an insecure person, or even jealous for that matter. However, for some reason I feel insecure, probably caused by the high regard I have for her.

I have realized, that my insecurity will some times cause me to act a bit like an asshole, and I would like to remedy it.

We are not talking about anything relationship-threatening, or anything serious, but I would like to change it none the less.

For example, I some times find myself taking control when there is a minor problem, so that I can “assert my dominance” so to speak, and distract from the fact that I actually feel a little insecure.

This can lead to me giving my girlfriend a bit of a hard time for 10 or 20 minutes while we debate something.

The relationship is going very well, we have an understanding and level of honest communication that I have never seen before. So this is not a desperate plea for help or anything, just some general advice to help modify my behavior a little.

Any time there is a problem, we always sit down and calmly talk about it in a reasonable and honest way. My girlfriend even knows that I feel a little insecure, because I have told her while issuing an apology or two.

I don’t even mind being a little insecure, I think it is normal after all. I just don’t want it to become a fuel for me to act like an ass.

I even know, that I don’t really have a reason to feel insecure, because it really is going so well.

Just I find it affecting me at the least expected time.

I am capable of allowing her to do things many other men would not, and I don’t get jealous or insecure. However, at very unexpected times, I will some times (often in retrospect) realize that it is having or had an affect on me.

For example:

If she hangs out with a male friend it does not bother me. If she wants to go in to the Chipendales strip club for a laugh next time we are in Soho London, I would be fine with it. I would even hope she enjoys it and has a good laugh.

However, if we are lost and trying to find our way some place. I may act like a retarded dominant ape, to get her to follow me. Because for some strange reason, I don’t want her to think I don’t know where I’m going.

I will then begin to give her a hard time, and tell her she has no idea how dangerous the underground is, and to just stick close to me and things like that.

(there are also other examples, probably better examples too, but I can’t think of any now)

Any tips on how I can stop being insecure, or at least not allow it to affect how I act?