My (39f) husband (39m) cheated on me 2 years ago and I forgave him.....now found out more details and am crushed.

2 years ago he had an affair and the other woman contacted me after he broke up with her. I moved out for a bit and honestly I've never experienced that level of soul-crushing betrayal. I was in absolute agony, realizing all the lies he had told to me.
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For a lot of reasons that I won't bore you with, I decided to try to make it work. I wasn't able to be intimate for nearly a year with him, and I was seeing a therapist for C-PTSD. It was truly awful, and it still is extremely challenging but we are both committed and working hard at our "new relationship".
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Last weekend, the other woman contacted me again. We hadn't spoken in 2 years since she originally told me (we spoke for about a week at that point and never again after that). She wanted to know if we were still together and when I said we were working through everything she asked if he had told me the truth about how long it had been going on.
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As far as I knew, it had been happening for 1 month. And it had started after we had a very bad fight about something. That's what I had always understood. We had this huge blow-out and in a state of anger he had reached out to her (they were Facebook friends) and it developed quickly from there.
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Instead, she showed me proof that it had been going on for many months prior to that. So it actually wasn't a result of this big fight we'd had. It had been happening all through many events.....our niece's graduation which we attended together and were happy at, our anniversary when we went away for the weekend, his grandfather's funeral, us purchasing a puppy together. So many memories. Instead, all the while he was with me he was also with her, telling her that we lived separate lives and were going to be divorcing.
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He points out that the end result is the same.....he made a terrible mistake and had an affair. He was weak and stupid and knows how badly he betrayed me. He wishes more than anything he could take it back. He loves me and is fully committed to me.
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But for me, it means I was living a lie much longer than I realized. And it wasn't precipitated by a fight.
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I don't know how to move forward. I don't know if I should move forward with him. To me, this makes him more of a monster than I originally thought. He claims no matter what the end result is he ****ed up and it's in the past. Who is right? Maybe I'm just not seeing clearly because of emotions.
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tldr: husband had an affair 2 years ago and I forgave him. Now I have information that it was months longer than I knew and I'm so upset all over again.


Source.