No-one can make someone cheat.
He says exactly what he thinks will work to get what he wants - manipulation. ‘My wife doesn’t understand me/we never have sex/our marriage is awful’ this is regularly not the case.
’The other woman threw herself at me/I was drunk/She shags all the men in the village’. He is likely to be telling you both lies. Woven in a little truth to assist with the cognitive dissonance. Cognitive dissonance may be why he is suffering mentally at present.
But All these ‘reasons’ do have one thing in common and that is it’s never the cheaters fault. They aren’t responsible. They only did it because of x or y or z. Sometimes they say ‘they did not dare say No to her advances because she may have gone and told you.’ This apparently demonstrates their thoughtfulness and benevolence. Showing he’s really a good man who was acting in other’s best interests.
He's a common garden cheater. This has NOTHING to do with you. You are not powerful enough to make someone cheat or remain faithful. It’s impossible. Cheating is all on the cheater. There is nothing my husband can do to make me cheat or remain faithful. I am faithful for me. My word is important to me. I do not cheat because I have to look at myself in the mirror for the rest of my days. And I want to like who I see. My husband is collateral damage to my choices.
Your husband will have other poor traits that allowed him to cheat. Requiring external validation, unable to take blame, poor self esteem, inability to self sooth, people pleasing, addiction issues, entitlement, knight in shining armour issues, poor integrity, maybe a lack of core values.
He has a but in his fidelity ‘I am faithful but not if my wife doesn’t know’ ‘I am faithful but not with an old mate’ ‘I am faithful but not if she comes into me’.
Op cheating can cause PTSD. You need to look after yourself. But this wasn’t and isn’t about you. You are the collateral damage to his poor choices. You are the prize here.
Many won’t agree but I would tell her partner. Tactfully and gracefully. But I would tell him. He deserves not to catch STDs. I would call him and give him the messages. If they are both scrabbling to save their relationships then less likely to go underground. Sometimes they then throw each other under the bus and you may get more truth via her partner.
Of course it may push them together but if that is the case you are better off ripping the plaster off quickly than realising it has gone underground in three years time.