I think working on that in individual therapy is a good practice ground. I would think it would be easier in individual with your trusted T in a safe place than in a group of people you don't know that well. So maybe the first step is getting good at this in individual therapy.

I thought the point of this particular group was not support with issues but learning more about how you interact with others, how they respond to you, etc. If this is correct, maybe you are expecting things from this group that they are not going to give, based on the type of group this is. If you want a different sort of a group, maybe your T could recommend one? If you want to keep with this group, perhaps not sharing such painful things would be better (save those for individual therapy) or changing your expectations might help. That probably doesn't sound too helpful, but I'm just wondering if you're expecting something from this group that it is not designed to provide? I also think that your question is a great one to ask your T. Maybe he has some ideas on how the group might help that you don't see, or maybe he can help clarify how the group is and what one can expect form them.

One thing that works for me, when I find myself wanting to retreat and pull away from T or not be open, is I think to myself "how would T behave if he were in this situation?" I know he would be open, forthcoming, non-judgmental, not defensive, curious, and eager to understand. So when I am talking to him and I find myself starting to retreat I try instead to be like he would be. I have had great results with this. Sometimes I have impressed myself so much that I leave therapy thinking, I can't believe I did that! This helps me in interactions with other people outside of therapy too. I also have made little rules for myself in therapy, such as I am not allowed to say "I don't know" in response to a question from T. There was one time I broke my rule and said "I don't know", and he shot back immediately, "you do too!" So I coughed it up. Sometimes it is just that I need time to think about it so I can figure it out, and he will give me space if I need it. Other times it is that I don't want to tell him, and I sometimes tell him that and he respects it.