I just want to throw out there, I am not saying not to say things to your psychologist, I think talking about things could be a really good idea! Just know that a lot of mental health professionals are mandatory reporters, and depending on where you live, your age, etc., there might not be a time limit on this. So it might help you first to look up either specifics of how reporting abuse works, or just ask your psychologist about it in that sense without bringing up that it happened. Like what would they do if a client brought it up. If that makes any sense?
So, I would try bringing it up in a very generic sense and say it is something you have never spoken about but seem to be struggling with. Hopefully your psychologist can help you talk about it in a way that feels safe to you, while also keeping in conduct with what they are required to do. I'm sure you could ask them about what types of things they are required to report. I know people have told me before as long as you do not give enough identifying information about the abuser, they cannot report it, and other similar things.
Best of luck.