I'll just give my two pence worth.
My ex cheated on me, like you a one night stand. He didn't confess. He mistakenly returned one of my missed calls (which I then missed) and left me a lengthy voicemail. I had to listen to it.
I moved on with him, I never forgave, and I never forgot. I was often triggered. Watching soaps, or stories of footballers etc. He swore he wouldn't do it again, couples Counselling the whole lot.
He left me in December 21 for another woman. By this point there were two children. One being a baby. He still didn't confess the OW and I found out about her later. He again swore it was only twice. My thoughts to that are, you don't cheat twice and get caught twice.
I never wanted to hear this when I was in your position. I thought I could do it. If I could give my younger self advice it would be to go. That if you go, I know it's scary and you don't know what the future holds, but he has just shown you exactly what your future looks like if you stay.
You will spend your time doing everything in your power to build a happy life, one that he wouldn't stray from again. You will have flash backs of this ons whilst your intimate with him.
You will endure this and you will never be completely sure of him again.
He may not stray again, but that doesn't matter, because you will never believe him anyway. In your mind, he will be with someone else every time he leaves the house for a night out with his friends. Every time he tells you he has a hangover, there will be a fleeting thought....'did you?' And you will never be sure, not because of you, but because he's planted that seed of doubt. That will take root. It's no life for the long term.
If I could make my choice again, I would have walked.
Of course this is your path to walk, and I am sure I may seem bitter, only two people know a romantic relationship and that's the two people in it. I just don't believe you ever move on from it.