During a window from 2018 to 2020, my wife and I were actively involved in EAs and I would later learn her's had become physical and I had no hint. Mine was only an EA, because the woman lives in another country and my wife can prove that I haven't been out of the country, but I consider my affair just as egregious as my wife's. At some point you clearly disconnected with each other and if it is like my wife and I, near simultaneous affairs, you miss a lot of signs...which is why I would say that when I learned that I was a BS it really hit me hard, simply because I had no reason to suspect anything.
Also, like your husband, after we got engaged, but before we were planning to marry, I ended up sleeping with a gal that I had been far too flirty with via text. As I look back on that whole thing now, I was engaged in an EA with this gal while engaged to be married, and it turned physical. My wife discovered that affair and were it not for her getting pregnant the next month, we may have gone our separate ways. The trauma from that whole thing certainly stuck with her and was part of the core trauma that lead her down the path towards an affair. I'm not excusing your infidelity, but your marriage got off to a pretty bumpy start with discovering your husband's affair and you were still newlyweds. Not dealing with that trauma and more or less what we call rugsweeping impacted you both. If he more or less got away with it, as what I like to think is a reformed cheater, he got away with it once, he just needs to get better at covering his tracks, so he may not have ever gone NC with this woman.
I only point this stuff out so you kind of begin to understand the last couple years of your life and framing events in their due context. At some point, my wife and I started talking to each other about whether we wanted to keep hurting each other or to go our separate ways. His cheating, your cheating, you've both hurt each other tremendously. You both have to heal and be willing to heal yourselves first before you can really focus at all on the relationship, or what still remains of your relationship.
Myself - BH & WH - Born 1985 Her - BW & WW - Born 1986
D-Day for WW's EA - October 2017D-Day no it turned PA - February 01, 2020