@Namechange20002 Honestly OP, please be careful taking advice and listening too much to Mumsnet.
It's all well and good the posters coming at your DH with pitchforks and encouraging you to leave him, but they don't have to deal with the very real life consequences of that. Especially as aside from this one incident you actually had a very happy marriage and family life.
In black and white, you'll end up a single mum of 3 young kids. Financially worse off, juggling a million plates on your own, your children devastated, you heartbroken. Maybe even having to move house or change work/hours.
Your husband loosing his entire family too.
Or maybe him even moving on quite quickly if he's a catch, leaving you in the trenches of single parenthood with small kids whilst he has lots of 'free time' to date and be happy (then unlikely to ever want to reconcile and come back).
And why? Because of some inappropriate messages sent to a female friend. It's not great no, it's very hurtful and embarrassing. But enough to put yourself and kids through turmoil, unending stress, financial ruin and single parenthood for the next 18 years or whatever? Nah.
Meanwhile all the posters telling you to end it have swanned off to the next thread from their comfy living rooms with a cup of tea.
Even telling you to kick him out for a few days. Okay, but who's then going to do the school runs, cook tea, sort the laundry, tidy the house, do bedtime routines etc. so he gets to go off and mope, evade everyday responsibilities and think about himself with free time, leaving you knackered in the trenches of everyday life, now managing it entirely alone and also devastated?
I'm not saying put up and shut up or accept poor behaviour. But it's easy to get caught up in the moment when your livid, not thinking clearly and you have a gang of online women behind you, cheering you on and awaiting updates for their entertainment. But this is your REAL life.
You'll even be discouraged by posters if you forgive him. If you post an update saying your working through things you'll often be met with 'id end it' 'he's lying' 'never trust him again' 'at least make him do xyz' 'but he wants an affair'.
Take onboard some advice applicable to you, but don't act on any of it until you've calmed down. Remember that everyone posting will not be dealing with any of the consequences of your real life decision.
Just something to remember xx