You are still really close to the day. Your anger and frustration is completely understandable.
The fact that you will have to coparent with this person who hurt you is going to make things difficult as well, I would strongly recommend counseling.
You will need guidance, that guidance really should be professional, because your feelings are going to be difficult to deal with.
None of us come through this unscathed. The problem with our children is we have to try to not let our scars affect them too much.
Having said that, what happened to you? Also happens to your child, your family, and your child will be affected by it. There's no way to avoid it.
My wife was affected by the infidelities of her parents, and the chaos that ensued.
We did everything we could to try to make sure that the children were protected from fallout from her affair. She was certain that they did not know.
It still happened however, it even turned out that one of our children knew that their mom cheated on me. This child was only seven years old when the cheating occurred, but as time passed, she pieced things together. As an older teen, and a young adult, she had figured out why mom had a man over during the day when daddy was at work.
Then, eventually, she started telling her adult siblings, and it was troubling them, all very young adults. One of them came to me and asked me about it when they were having emotional difficulties of their own after a break up.
I did not directly address it, I spoke to my wife first, and then she spoke to all of them about her behavior.