I am a BS, that said, I feel badly for you and for him. I don't truly understand the "fog" having never been on that side of things, but I do understand the concept of the fantasy/escape.
I agree with others who say despite the problems in the marriage, the choice to seek validation and have an A is only yours to own, and it sounds like you are, so I commend you for that.
Gosh honestly I don’t know but I do know I don’t want to try and dissect him if he’s not willing to open up. I do think he needs to figure himself
Sadly, I feel like there needs to be some dissection and open dialogue to heal and move forward. It needs to be vulnerable, painful and honest. It sucks, but ignoring it does not actually move you forward.
I am new to this journey, but having been on the betrayed side, I don't believe I could be moving forward without discussing and really feeling and processing the plethora of emotions I have felt over the last few months. I can't imagine your H is not feeling those emotions and believe he isn't really going to be able to move through it with any sort of depth and healing until he does.
I have read other forums where BS made drastic changes/ended their marriages on the spot as a result of betrayal...but they still experienced emotion and grieved what they lost. That is the human experience, to feel. Your H history of PTSD may be playing a role in this.
I am also concerned with your language use that you had an accidental threesome...perhaps an unexpected or unsolicited threesome, but at some point in that, you had a choice to engage and it sounds as though you did so because you saw that your H was turned on by it (maybe I don't travel in those circles, but it seems pretty forward to come into a bedroom and start kissing someone you don't know...have you asked your H if that was planned ahead of time?)
What you choose to do sexually is your call, but regardless of your choice to have an A, you still have a seat at the table in exploring how you and your H can move your intimacy along and what you do or do not want to do sexually. My strong bias is towards healing the two of you first, without complicating things by adding new partners.
Good luck. Open, honest communication, though likely uncomfortable, is I think critical for you both and support in IC will help you both navigate this winding, undulating road.
[This message edited by hopeandhealing at 10:08 AM, May 7th (Monday)]