I realise that I have childhood sexual trauma

I'm a sixteen year old, trans ftm and for the first time I realised what really happened to me. I've always joked about having sexual trauma with my friends, in the same way I'm able to joke about my sh (self harm). About a month ago, I was pretending to have a parter and was talking to myself as if I was talking to someone else.

I spoke to myself in depth about that trauma, and as I went through it bit by bit I began to really realise what had happened to me, and by the end of it I was in tears. Don't want to go too much into detail but as a kid, maybe around seven, I had this game with my friend who was the same age, maybe a year older, where she would pretend to be whatever boy I had a crush on at school and we'd run away together. It started off with kissing, then with tongue, then the next thing I remember is her fingering me. I had never really taken this as serious because it was all still a game to me, and I feel like it's my fault anyway. I know I was a child, but never once did I say no, and I remember being the one always asking to play.

The reason I'm writing this is because beyond the jokes with my friends, I have never gone into detail about it with anyone, and even my parents don't know. It feels like a betrayal to my mum because when she was a kid her stepdad touched her, and I let someone do it to me willingly and kept it a secret from her. Even just thinking about it now causes a break down, and I seriously don't know what to do. I probably need professional help, but I can't even tell my friends who I tell everything about what happened to me.

I'm trying to make this my first step in opening up about it.