I read him a letter explaining that I sometimes manipulate people by saying things that I'm saying because I want them to care about me and be upset by. Like saying how much I hate myself or hurting myself. I'm not lying, but I'm saying it because I want them to display some emotion in response to it so I feel like I matter.
He didn't think that that makes me a horrible person.

He thinks I internalize shame and guilt about wanting to be cared about because my mother didn't provide that when I wanted it as a kid and she thought emotions were stupid. I'm oversimplifying of course, and it was my choice to hide how sensitive I was and hide my emotions so she wouldn't feel bad, and she was in a really bad emotional place and my father was emotionally abusive. And instead of being mad at my mom I came to believe that the problem was with me for wanting things in the first place.
He wants me to write an unsent "anger letter." I don't feel angry at my mom though. I understand that her intentions were good and she wasn't emotionally equipped and she feels bad enough already. He wants me to let myself feel angry with her, but I'm not suppressing anger towards her, there really isn't anger there.
He was surprised to find out that I don't really care about children. He was asking me if a 7 year old that I had come to care about showed me some art they did that they were proud of or something, wouldn't I care and tell them they did a good job and stuff? Would I think their stuff was stupid? And I was like "honestly, yeah." I explained that I'd think it was stupid. I'd humor the kid and pretend to care and act impressed because it would be cruel not to. I don't want children to be unhappy or suffer, and I care about their feelings. But no, when I interact with children I'm usually annoyed and really don't care about their story about a princess on a pink unicorn or whatever. I never let it show. Kids like me and people who know I don't like kids who later see me interact with kids are always surprised by how good I am with kids.
So, no, I don't fault my mom for not caring about this kind of stuff. But she never really felt the need to hide it and didn't understand that it was important to me that she at least pretend to care. And she's bad at pretending to like something she doesn't like, so I just don't show her things I'm proud of.
But I pointed out that I know this about myself and I wouldn't have children, and one of the many reasons is that it wouldn't be fair to the kid because I couldn't provide the kind of emotional support and stuff that they need. It's the same reason I don't have a dog. Unlike children, I actually like dogs, but I know that with the hours I work it wouldn't be fair to the dog for me to have them because I'm not able to give them what they need.
He was definitely caught off guard by the fact that I don't like children or care about the stuff that's important to them. Of all the things I told him today, I think that one probably surprised him the most. And it's one of the things that I actually don't feel guilt or shame about.

I sat on the floor again hugging my knees and facing to the side and kind of hiding. He commented at the end that the chair would be more comfortable. I told him that I felt safer on the floor. He made some comment that made it seem like he thought that I felt like I didn't deserve to sit in the chair or something, and I tried to explain that it really did make me it easier when I sit on the floor and that I'm 23, so I'm young enough that it's not really uncomfortable. He didn't seem to really get it.

Edit: okay so maybe there is actually some anger there once I start writing... But what's the point? It's not constructive or useful. It won't change the past.