New Therapist

I've been to about 4 sessions with my therapist now and am finding her alot better than my previous one(she was very very bad). She's letting me take things at my own pace and working on building up a trust with her which is good. She still doesn't know what happened to me, she knows that a trauma occurred 7 months ago but doesn't know anything more than that although I'm sure she has guessed. 


I can't seem to tell her what happened I can't even admit to myself what happened, I just can't say it. As the sessions go on they get a bit more in depth and I'm happy with the pace of it but surely I should be starting to tell her what exactly the trauma is so I can work through it?? 


I don't know how I would start it, I asked her today what she needed from me in order to help me keep taking steps forward however small and she said that I was in the driving seat and it was up to me what speed I want to go at but for me to think this week about what I would like to talk about next week but I just don't know how to just spit it out I just panic at the thought of it and I know I'm going to have to at some stage. I know that's going to be the most difficult part the thought of talking about it just sends me into a panic, like I'm back there again. Will I ever feel safe again?