I definitely try to make myself talk to T about difficult things. But as I am not that long with him yet almost everything feels difficult. Things I can't talk about I try to write down and send him a mail. Sometimes still I can't talk about the mail then. My problem is that if I push myself to hard I end up dissociating though.

Trust is something that can't be really pushed. It happens over time, gradually builds up as you return to your T week after week and you see he is there every week, he stays kind and listens and doesn't react weird even with the difficult stuff.
Sometimes trust can get a boost, too... when you have one of those situations where the relationship has to prove itself.

I just had that happen with my T. And it has changed a lot about the way that I think and feel about T. I am already curious to see T again and to see how it will affect the way I can open up to him.