First you are very early on. I am 1 year out from my DD.
I am pleased you and your husband had HB sex....we did not. I have read others on here that had HB sex and said it fed each others love for one another enough to carry them through the drought you are in, and I am in.
Sex after an affair is tough...maybe the toughest to overcome...and I think particularly so for women.
There is some truth to the joke that when it comes to sex women need a reason, men just need a place.
I struggle with that "joke" because my wife had sex with a guy she barely knew....still waiting to understand how this could have been an option for her.
Your husbands case...where it was an old GF...differs from my case. Not sure how much time they spent together (he COULD know her pretty well)...and I don't have a timeline on my wifes affair either...but I estimate my wife had about 90-120 hours invested in her relationship with her AP, start to finish. That is actual time I think they spent together, including the minutes they used for texting.
I am sure she was thinking about him almost constantly during parts of her affair, but actual time spent "getting to know him" was in that range. Of course, you can "see" a person by projecting what you want into them...even when they are not present. But actual face time is what I am referring to.
Obviously an affair is not a healthy relationship...so no "normal" rules apply.
I continue to wrestle with how my wife had enough "motivation" to go through with her affair. Actually, when it went from EA to PA we were in weekly MC sessions and, at that time, I suspect she had 30-50 hours face time with her AP.
My wifes A followed the passing of a loved one...it appears to both of us that was the start of our downward tumble...we had issues before that, but can both track back to when things really got unbalanced (namely my anxiety and her detachment...both fed on each other). I see your husband lost loved ones too just before his A. I have read this could be a triggering event for A to blossom.
I initiate sex mostly. When my wife declines, I am okay with it. I like to think I am not pressing her, but I think that is only a partial truth. The other side is that it saves me from having to stop in the middle because of the pain of the affair....I almost instantly go....well, you know...not able to continue physically.
So a part of me doesn't mind because I don't want to feel any more rejection...rejection from either of us.
Kind of rambling.
I am formulating a post on "fear"...think it ties into sex. Might check it out, see if I am close to a truth.
You are so close to DD...be as easy on yourself as you can be. What you feel NOW will change....you will see and feel the roller coaster of emotions others on here speak about. Dont freak out that your fWH is not on that same ride. This is trauma for you, it is painful for him...there IS a difference.
God be with us all.