You are describing a lot of what I went through in those first months.
I am about ten months out now, and at three months I was still very much living inside the blast zone. I could function, work, parent, have conversations, but underneath all of it my brain was constantly running. What happened? Why did it happen? What did I miss? What else don't I know? What was real? What does this mean about our marriage? Can this be fixed? Do I even want it fixed?
I read books. I read forums. I analyzed conversations to death. I asked questions over and over from slightly different angles.
For me, a big realization was that I was trying to think my way out of something that couldn't be solved entirely by thinking. Listen to the people here that have been here for a while.
There is absolutely value in understanding the affair, understanding yourself, understanding the marriage, and understanding what was happening inside your husband. But there came a point where I realized I was subconsciously searching for the one missing piece of information that would suddenly make all of this make sense and stop hurting.
I never found that magic piece.
What I did slowly find was perspective.
Three months is so incredibly early. I know that probably isn't comforting when every day feels about six weeks long, but you do not need to have your marriage figured out right now. You don't need to know whether you are going to reconcile forever. You don't need to know exactly how much of his resentment was legitimate, how much was distorted, or what every revelation means for your future.
You can just deal with today.
Also, please be careful not to let his bottled up resentment become an explanation that somehow turns into responsibility being placed on you for his affair. There may have been real problems in your marriage. There may be things you eventually look back on and wish you had done differently. I certainly found things in myself and in my marriage that I needed to examine. But marital problems are shared problems. An affair is a decision made by the person who has it. Both things can be true at the same time.
One of the hardest things I have had to learn is that healing is not linear at all. I have had days where I thought, "okay, I am finally getting somewhere," followed almost immediately by days where something tiny knocked me flat again. Then gradually the terrible days became terrible hours. Sometimes now they are terrible days followed by better days.
That is progress, even when it doesn't feel like it.
And all of the reading, therapy and introspection can be valuable, but give yourself permission to occasionally stop studying your own trauma. You don't have to spend every available hour becoming the world's foremost expert on betrayal. Watch something stupid, go outside, have coffee with somebody. Do something with your hands, give your brain an hour where its only job is to exist.
You are not failing because you are still crying at three months. You are not supposed to have metabolized something this enormous already.
Take what you can from therapy, books, forums, AI and people who have walked this road before you, but don't feel like you have to discover the entire answer immediately.
Sometimes the most honest answer really is:
I don't know yet.
I have become much more comfortable with that answer than I was in the beginning.
Take it a day at a time. Sometimes an hour at a time if that is all you've got. Eventually you will look back and realize that somewhere along the way you stopped drowning and started swimming, even if you cannot identify the exact day it happened.