A lot of people have said many good things about trust:

You have to take a leap - jump in!
You can decide to trust - just do it!

Trust has to earned - take your time
Trust has to be learned - take your time

I think that as with so many things it is individual, each will have to find their own way.

However, a few general comments have come up in my head by reading the thread;

Crushers rose's quotation is beautiful, but sometimes you have to blow gently on the rose before it can defrost and bloom.

I think trust problems might also be because we go in a wrong direction, towards an ideal that is not what the soul really wants. Thinking it over again might be the thing. Hunger can make some fantasies very hot, while the real reality so to speak is not what is wanted, or not wanted now.

Finding a Dom does not, unfortunately, mean that your needs overlap 100%. That would nothing short of a miracle, though they do happen :-) But often you have to work with what you have till you find the right kind of way that both can find fulfillment in.

Trust: I do not think that trust is a matter of will, it is a feeling and you cannot control feelings. You can control your actions, though, and how you want to respond to the feelings.
What you can do is jump in with fear and all, hoping all will be well. And as Desperado says, if it is, you have trust.

As for becoming a switch as a defense mechanism, I do not think that it in general works that way. You do not become a sub as a defense mechanism, or a Dom, or a switch, it is just what you are. My guess would be that feeling like that might be a sign that you are either trying to go faster than you really can, or in the wrong direction, and part of you is trying to feel safe.