My partner was unfaithful 5 years ago. It was a ONS, followed 6 weeks later by an attempted liaison. We had been together mostly happily for 18 years, however at that point in our relationship things were not so good. I had been suffering PND, we constantly sniped at each other and had 'competitive tiredness'.
I knew something was up after the OND, he confessed 6 weeks later after failing to woo another woman on a night out. Sadly he chickened out and only told me part of the story ' I am not sure if I love you any more', then 'I met someone I really liked, but nothing happened, then they just kissed etc etc.
It was the lying that really broke me. If he had just said, "pastry I was feeling shit, drunk and lonely, this pretty young woman chatted me up and we ended up having a dirty fuck, I haven't seen or spoken to her since, I don't even know her name". It would have been so much easier than having to wrench the truth out and initially believe there had been some kind of real connection other than his dick.
At the time I was heartbroken and suffering depression and couldn't face the thought of going it alone, we went to marriage counselling (didn't help me much) and things were very up and down , but to his credit he tried really hard to make amends, took the screaming and shouting.
After about 18months I changed mind and started looking into where I stood if we were to separate and looking after myself, getting my social life back, taking up hobbies. Oddly feeling more empowered I decided that I would stay.
Nowadays our relationship is fairly good, we talk our feelings through and work well as a team and enjoy each others company immensely, but it will never be the same. I have a deep sadness and dissapointment that he is not the strong man I used to think he was. I also keep a little piece of my heart back, just in case.
It's still very early days for you OP. My advice with hindsight would be to try and have some time away to clear your head. Find out your options financially and housing wise should you decide to split and know that you don't have to rush to any decisions. 💐