Ok, just had some moments of clarity that I thought I would share just in case it helps someone else.
They "Why" question. Its a hard one to answer and if your "why" is ever about any other person, than you aren't on the right track. So here is my "why".
Before the A and my BH was just my H, he was very distant and non-participatory in our relationship (I do not say this to lay blame, but as factual and important to explain MY failings). Here is where my mistakes began. I thought that this was all about ME. His lack of love for me, or keeping up his end of the marriage vows, etc. I completely FAILED to see that he was dealing with is own emotional issues that had nothing to do with our marriage. I failed to see a hurting person, I failed to have empathy for his experience. All I could see was MY hurt and MY anger.
So I pursued....relentlessly initiated- talking, sex, intimacy of any kind. Sometimes I was successful. Most of the time I was left hurt. But that was the LAST think my husband needed from me. So he pushed away more and more. So I got angrier, and saw him for the person he is less and less. All he heard from me was disappointment and judgement.
I seriously thought that I was the only one working on my marriage, when I wasn't "working" at all. I was tearing it apart. I was trying to get my needs met, so consumed by rejection and fury that I couldn't see the person sitting right in front of me. I had no clue about selflessly looking to see what he needed. I was so ignorant, I thought he just didn't care. And I gave up. Not in one instance. Never fully realizing it. But I had.
So that led to my selfish decision. Because I made the whole thing about me. I became so angry that empathy was impossible. And now that I see the big picture, how shitty to hurt someone who already so wounded.