I'll try to sum it up for you; this was all over 2 years ago now.
My H began to change in many ways. He definitely acted manic, sometimes angry at me, things that indicated he wasn't "right". When I discovered the ow he was already several months into the affair. He promptly moved out, but not to live with ow. It is my understanding that he never actually lived with her, but I am quite sure she spent the night with him on many occasions.
No, he did not say I was too busy for him or neglectful. He just said he didn't want to be married to anyone; that he needed to recapture his youth; he got married too young in life; he was very unhappy with his job. My understanding of it now was that his depression had blocked his feelings for me and there was no passion, no attraction for me anymore-thus, the ow being in the picture. She was the epitome of affairing down, and yet he was addicted to her like a drug.
He was only mean and spewing at me if I tried to get him to come home, talk about "us" or tell him he was making a mistake (this all during replay). He was a drop-in; never stayed away for too long a period of time before a phone call or a visit.
He was adamant that he was "never coming back". But, he never filed for a divorce and we are still only separated now.
He would, about every 6 weeks like clockwork, have a huge fallout with the ow and come home for a day or two, saying what a huge mistake he'd made...but then the drug-like withdrawal symptoms would kick in and he'd be off running once again. This was the worst of it for me, as it kept me hoping falsely and continuing on a terrible emotional rollercoaster that made me very sick, both physically and emotionally. I am well glad to be off of it.
Hope that helped somewhat.
Most of us really marry only once. First love endures, even unto our dying day. And we never really divorce.