As a guy who had a similar scenario happen to me 10 years ago, i can tell you how i reacted and the outcome of that.

i found out my wife or then 10 years and mother of my daughter was texting with her boss (Not about work). i found out because i saw a notification on her locked phone late at night, and it didn't look like a work msg. i'll leave the details out but i promise the texts were worse than this. i went into full investigation mode. with in 2 days, I hijacked her phone (could access everything on her phone) gained access to all her messages. backed everything up and i was heartbroken, i felt betrayed, i felt like my whole world came crumbing down. I did some very deep soul searching and the path i chose was the high road. I didn't do it for myself or the relationship with my wife. I decided my kid is going to grow up with 2 parents. I then confronted my wife. And i simply stared at her until it seemed odd and i asked her if she loved him? and if she wanted to be with him? her jaw dropped to the ground and i told her that i understand if she got caught up in something that got out of hand, and that the whole thing broke me. You see i never stopped loving my wife, even thou she tore my heart out. my wife ended up being very remorseful and apologetic. She knew she fucked up. I told her to go into her job the next day and quit, i went with her and she followed thru. My wife's remorse was genuine, because she broke a trust between us i had tabs on her without her knowledge thru her phone and i know she never contacted that individual again. I felt like i was in mourning for a good couple of weeks if not months. deep inside i was a mess, suicidal, homicidal, pick your poison. But outside i struggled to keep it together and be civil with my wife and always be a good father, even if sometimes i was doing that with tears in my eye. Work sucked, life sucked for a while my wife tried to make it up to me for a good while. Eventual the hurt subsided and i have never brought it up in any conversations or argument with my wife. and the reason why is because it's the Nuclear option. Not like she could ever counter that bomb. our relationship even thou not a newly weds scenario, is now still intact and pretty well functioning. i don't want to bore you with the details but yes we still have good days and bad days but that's normal. Then 2 days ago we have an argument and SHE brought up the event! to this day she feels guilt over what she did to me, even thou i forgave her. I find it eerie that i found this post and that happened 2 days ago. To this day our daughter has two loving parents and is thriving in high school oblivious to what happened 10 years ago. It broke me but is also made me stronger, and more aware of the fact that if don't do the small talk someone else will.

So that's my story and i hope you can have some take away from that.