Early on, I wanted to tell him, but I was advised not to
That sounds like me on DDay1. I got lots of advice not to tell. Many from various professionals. And, like you, it didn't sit right with me. In fact, it haunted me greatly. As I struggled, I wrote down what I wanted to say and revised it frequently. And researched him. Until I found his work address and business cell.
Yadda, yadda, yadda, DDay2 came just over a year later. When I discovered it, I had my script ready. My hands shook so much while I dialed that number, I mis-dialed it twice. Then I must have gotten it right, as a voice answered "Hello this is Mr. LTAP" and I read my script. It went like this:
"My name is Chaos. Your wife LTAP and my husband Mr. Chaos are having an affair. It was originally discovered in 2017 and I just found out today it is still going on. I should have told you sooner. I am very sorry"
And he said words that both did not surprise me yet shocked me to my core "you aren't the first upset wife I've ever talked to"
We spend the next few days sharing details. Truth be told - my voice shook the whole time and I puked in the bushes after we hung up.
I share my story, not to make it "all about Chaos" but to let you know you are not alone. And not telling is not sitting right with you because you know it the wrong thing to do. People deserve truth in their lives. The weight of you holding that truth and keeping it from OBS is crushing.
In fact, I even had a letter written with a slight variation of what I actually said to him, and a few photos, ready to have sent Certified and Restricted (where only OBS could sign and receive) to his place of business. Sadly, I caught them communicating before I could have it sent.
Now, when (see what I did there) you do tell - don't let anyone know you are going to do this. They have a way of talking you out of it and/or getting their cover story in place.
Sending you courage and strength.