Hello and welcome. It takes a lot of courage to finally post and I'm glad that you did.
We recently had another member here who self-disclosed his A. I told him what I'm going to tell you. I wish I had had the courage to do the same.
I was a serial cheater. I had what I too swore was "the last one" (long PA) that ended in November of 2018. A few days after it ended, I dressed for work but called in sick. Drove around aimlessly for most of the morning before stopping at a local park to finally make the phone call to my employer's EAP (employee assistance program). I ending up making my initial appointment with my therapist that day, whom I'm still with all these years later. In fact, I'm seeing him today for my monthly check-in.
IC was really brutal at first, having to face the man in the mirror for the first time in my life. Those weekly sessions were tough and I really wasn't listening because my mind was still in the fog and insanity of my double life. I was continuing to speak with a longtime EAP off and on while trying to work on myself. Needless to say, that wasn't going well.
Fast forward a month and I was back on Tinder just before Christmas. Started another brief PA with a married AP (so much for the previous PA being "the last one"). I was sitting in so much pain (pain of my own making), ignoring my therapist and trying to self-medicate with my usual avoidant tendencies. That PA ended just after New Year's but I was still talking off and on with my longtime EAP.
The EA ended in May when I finally cut things off and went NC. The fog had been lifting for some time and I finally got my head out of my ass. My therapist had been pushing me hard to self-disclose to my BW but good ol' cowardly, avoidant Skip was refusing to do so. I kept rationalizing that I was 'preparing myself' but I was simply too terrified to tell her.
Well, my scorned EAP did it for me with an anonymous letter addressed to my BW. I was confronted with it on D-Day and my entire secret world, as well as our marriage at that time, went up in flames.
My wife has stated that there were 2 things that helped her decide to give me a chance at R: 1) I was already in IC for 6 months at the time and she was finally starting to see changes in my actions and 2) I confessed and timelined EVERYTHING on D-Day and in the immediate days after.
But she also said that she wished I would have told her myself. Getting that letter from EAP was beyond devastating and she had to sit with it for a few days before confronting me because of how gutting it was.
All of this to say: Please don't carry this around or think you will somehow carry it to the grave. The truth will out. It always does. Find yourself an IC who can guide you and don't drag your feet like I did.
I wish you and your BH healing and peace.