I'm curious-- why did you leave such a big thing out when posting here? I'm glad you finally feel open to sharing about it and I hope it helps to know that there are so many of us on here that are dealing with As too. Were you worried about what people would say?
It makes sense, fits with his behavior in the fall, also why it might have been harder for him to come back (scared of what he'd done, how you'd take it). Glad that you guys are working through it though-- that's great.
I thought a lot about why I left it out before the new update (and was ruminating on it for weeks, but am still working during this time and also working a side job, in addition to IC/MC, and writing my journal). I think there are 2 things at play:
1. I was so, so, so tired of defending my H to my friends and even my IC, and ultimately saw this as a place where I'd have to defend him again. I'd say this is 80%. Tired of defending my decision to stay when he had left, tired of defending waiting for him. See more below. My friends do not know about the dating while separated, but I was still having to back him up/defend his choice about coming back, that it felt like a huge emotional wall to climb, especially to strangers on the internet, even though I do not think I'd need to defend his actions here. I do sometimes see people be challenged and know it's for their own good, and wasn't sure if I could handle it. However, if anyone understands, it's the people on these boards, and everyone is supportive of each other.
2. I had agreed with him that I would not disclose this to anyone except our ICs and MCs. This was my choice, not something that he asked me to do. If I am preaching honesty, I felt not great about not honoring that. Since then, we have had a lot of talks about productive outlets/friends of the marriage and where to get support, so feel OK here.
I felt like I was constantly having to explain/describe H's behavior about leaving IRL and then also having to explain him coming back, and honestly was just incredibly overwhelmed by this. I don't think I was worried about what people here would say. I was/am embarrassed about how I found out, also. I wasn't in denial about what happened - and felt immersed in it a lot, but also compounded by dealing with him leaving, what he did when he left, and what lead up to him leaving. I was spending so much emotional energy talking to him about it ad nauseum that it was just easier to leave out here? That is maybe 5% of why I didn't?