I don't mean to make you feel badly at all-- I know for me this is the hardest thing I've ever dealt with. (I really, really hope this is the hardest thing I ever have to deal with.) So I totally get it, I've been there too. Broke every DB rule and then someone here told me to just brush myself off and get back on the horse! So here I am, telling you the same.
I think one of the hardest things with DBing is that these behaviors and interactions are totally ingrained. You've literally been doing them for DECADES. It is incredibly difficult to stop. Some of the vets say your S has "fired you" as their wife... I hated that, and I think it is sometimes harder for those of us who have Ss who don't just walk out the door without a backwards look. But it's true. They no longer see us as they once did. The moment they started the A they metaphorically took off their wedding rings and started a new relationship, even though they can't quite let go of us either.
It is hard to live in the same house and DB. It is a choice you make (and one that I've made, so I totally get it) but it means you need to be on all the time, always monitoring your own actions and responses, pasting a smile on your face when you don't feel it, dressing up and getting out of the house even if it means you just drive to the store and eat popcorn in the parking lot with makeup on. Start small and just keep going. You've got this.
M
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing