Not a word to anyone, but I had an affair with a coworker.
How did that happen?
We just kept hanging out and our relationship blossomed from there.
You shouldn't have a sexual relationship with a coworker due to how frequently they lead to workplace drama. It's easier if you just don't break the trust of your romantic partner as well by leading this affair.
I'm an adult so I can do whatever I want, especially when it's consensual.
It wasn't consensual with your S.O. Then there's the potential drama at work. Imagine how you'd feel if the roles were reversed with you and your S.O.