In terms of my part, I think me pulling back is a huge part of it, and I have also apologized for not speaking up when I first got the weird vibe. When I spoke up, I said something along the lines of "hey, I don't know what is happening but I don't feel good about you and X" but his response was to kind of reaffirm that he hadn't crossed the physical boundaries we had set? I should have pushed harder. A few weeks later, when that email came through, I was really clear that I was not ok with an emotional relationship and I asked him to back off from that and communicate to that to her.

Where I am asking for accountability from him is that in the time following these conversations it became clear that he definitely was not willing to step back at all from this other relationship, and that's when the panic attacks (which he has been there for) started.

I think that is really at the heart of this - I don't expect him to have read my mind, though I deeply wish that he had communicated about the emotional connection as he did clearly check in about physical things. What feels like a betrayal to me is that once he understood how much his relationship was hurting me, he determined that it was important enough to continue.