My ExH cheated on me four months into our marriage, but I knew nothing about it as I was rather distracted being treated for a chronic condition in hospital. He then confessed, because he couldn't live with the guilt and promised to never do it again. I took him back, partly because I thought it was my fault for daring to be ill. He then fell into a pattern over the coming years of having affairs, confessing to me but changing the reasons why he did it. These reasons were always my fault. I was fat, I was dowdy, I was too demanding of him with the kids, I was shrill, and finally, the best one after all that, I was too preoccupied with the degree I was doing to get back into workforce and make a bigger financial contribution to family finances and he felt neglected.
Did I know he was cheating? In the early days, not explicitly, but was aware things weren't quite right, but always thought it was my fault anyway and pleased he didn't leave me. Pathetic eh? The final affair came when I was at Uni and my reaction was totally different. I found evidence, called him out on it and made him admit this was totally unacceptable. Even so, I still stayed as I didn't want my DDs 'to come from a broken home'.
I finally found the courage to send him packing when, having found a backbone I started to call out his other EA behaviours, he then started to pick on my then 14yo DD. Finding myself standing between him and her to stop him knocking her block off caused the scales to fall from my eyes at last.
I had finally realised that staying 'for the sake of the children' was doing my 2 DDs no good as I was teaching them to be complicit in his abuse. I didn't want that for my DDs.
I started divorce proceedings and have never looked back. No regrets apart from one that I should have left years before.