This happened to me about 10 years ago. We had been together about 15 years at that point, and were going through a particularly rough time with his father's dementia. My husband was his sole caretaker and had been for years at that point so it was difficult but no problems, that I knew of, between us.
Any way, he was having problems with his computer and I thought late one night after he'd gone to bed....hey, I'll fix it as a surprise. I got the surprise. He had left his email up and I discovered he was on a dating web site and had been contacting several women. He was basically pretending to be someone else, another type of guy, I guess.
I went through the roof right there and then. I woke him up and started raising hell with him. He was stunned that I found out and didn't know what to say. I just kept screaming at him. To be perfectly honest, I don't even remember much more than that. He could not explain himself. From reading what he wrote I could tell he was having some on line fantasies. He said he never met any of these women and I believe him. Frankly....I don't think they were particularly interested. It was more like a romantic than sexual thing (no dic pic) . I started going through his phone after that too and discovered a long term long distance EA with a former GF. He was sending her gifts, much nicer than ones he gave me, and romantic sayings that he never said to me. Basically he was giving all the romantic feelings he had to other women. The EA hurt me more than the online stuff.
So how did it turn out? Well, he stopped doing the online stuff and eventually I stopped checking. I think I just no longer cared. I did check his phone about the EA periodically and I could see that had changed as well, not stopped but changed. I figured the hell with it, she's on the other side of the country and he knew her long before he knew me. Although I have a terrible temper, I'm not jealous by nature. I do still get triggered though when he spends too much time (IMO) talking to attractive neighbor ladies, things like that, but I know there's nothing there. He can't really perform now anyway, which I'm relieved by.
Our relationship did change after I discovered this. All my romantic feelings for him died. They just died. Never came back. I have no sexual interest in him at all and we rarely even attempt it, thank God. Of course, I'm nearly 70 so that's part of it, I'm sure. Mainly I have serious health and financial problems which is why I stay. If I had the money - then or now - I would have left. I would still leave if I had the money. I'm fond of him, I love him as a friend, but I have not had any romantic feelings towards him since that time and it really did diminish my respect for him.
I'm just telling you my feelings, neither of us went for any counseling on this - that costs money - and maybe neither of us at that point realized the damage this did. I think we both spackled it over because we had so many other crises to get through. Family problems, he had a big health crisis, I've had health crises, then COVID, and now the current financial crisis (which it is, IMO). We've just been lurching from crisis to crisis for years.
As to what you should do, first take copies of everything you've seen if you haven't already. I would schedule an STI test just to be sure on your behalf. You don't know all he's done.
The next step is to start the talk. I don't know if there's any good time for this, maybe after making him a nice meal to make him feel comfortable and reassured and afterwards I would start off by asking him questions. "Honey, you seem kind of different lately - more detached." Some bullshit like this. Are you happy with our marriage? Have you been thinking at all about other women?
Yeah, I know that's a bomb but for me, putting it in a question format rather than telling him "I Know" gives him room to either tell the truth...or to lie. If he lies, then you know more about him. You know he's willing to lie to your face. He's willing to keep hiding it. You can maybe judge other things by how he answers. You can't lose your cool though, you have to be very concerned and conversational. My point would be to see if he explains himself or reveals anything or how he handles it. THAT WILL TELL YOU A LOT.
Then the confrontation:
If he comes out and tells you the truth, whatever it is, there might be more than you know, you can take it from there. At least he's been somewhat honest. Maybe there's something to work with. If he lies....well, you have a liar. Then I would tell him exactly what you've seen - show and tell time. I'd ask him to explain this. See what he says. Now, I can't tell you to be calm - I was about as calm as the French Revolution, but it's better if you can be calm. Cry it out or yell or whatever before he gets home, try to get it out of your system first if you think you're gonna lose it. It's okay to be angry but at this point you want info and want to be able to assess him and it's harder to do that when you're just blasting your feelings at him. The more you blast, the more he's likely to shut down. Try to give him enough emotional space to explain what and why he is doing this and the bigger question: Did you meet any of these women?
See what he says. Whether you can believe it or not, I don't know. I wouldn't automatically believe anything he says. This is a long road here, the confrontation is the first step but it's a long road after that. I would tell him this is completely unacceptable, you want it to end immediately, these profiles have to stop and you will be monitoring. You have the absolute right to set up boundaries and expectations AND TO SNOOP - no apologies for snooping! There is some privacy in marriage but NO SECRECY. Do not be afraid to think of or discuss divorce. In fact, I would urge you to see a lawyer to see what it would look like for you, it will put you in a stronger, more confident position.
When they start cheating, you don't know how bad it's been, or how bad it might get. It definitely indicates there is something wrong in him, something he wants, something he's missing, My husband was looking for a way out from the grind he was in but he didn't seek it with me - I guess he wanted to re-invent himself. Well, it destroyed our marriage, IMO, and as I say, if I had the money and health I would leave NOW despite my fondness for him. And this happened 10 years ago so...this doesn't necessarily go away and you might not be able to fix it. Be brave and realize that in the end, you are enough in and of yourself, and YOU ARE NOT TO BLAME FOR THIS AT ALL. This is totally on him.
Stay with us, there are great people on here and you'll get good advice and support. I would advise you to keep a journal of your own - in a secret place - because one of the things that strikes me the most 10 years later is how little I remember other than the initial shock. I would NEVER have expected him to do this, never. I'm surprised at how little I remember after the confrontation. I think sometimes we have some weird form of protective amnesia. So journaling might help you to keep track of things.
Good luck! Nobody wants to be in this position, but I think it's best to deal with it head on and come to your own conclusions about how you want to live YOUR LIFE and what you want out of marriage. Don't take any shit off him.