I was the other man

I had an affair with a married woman I worked with. She told me her husband was cheating on her and went on about what an ass he was and that they hadn’t had sex in a year. I was single and fell in love with her fast.
She said she was going to leave him but after a year I realized she wasn’t going to but I kept seeing her. Then one day she texted me and said her husband had found out about our affair and we had to stop seeing each other for just a little while. I was heartbroken but respected her wishes.
A few months later she texted and said she had finally left him and wanted to move in with me. After a messy divorce we got married and I was happier than I had ever been. A year later I caught her having sex with this guy right in our bed when I came home early from work.
I found out then that it was her husband that kicked her out when he found out about not me but this guy I had caught her in bed with. She was having an affair with him at the same time I was having an affair with her while she was still married. I also found out she never stopped having sex with her husband during all that time. I found that out by contacting her ex after catching her fucking this other guy. And they had an open marriage, something she never told me about.
I asked why divorce her if they had an open marriage. He said because she lied to him, her son wasn’t really his. Now she is pregnant again and I truly have no idea if I am the father.