My OH had a 2 year emotional affair. But that's another story.
Up until the moment I realised I had NO idea. It wasn't on my radar at all. Really No idea.
I simply saw a phone message that said "are you awake yet?".
And then a load of tiny things like phone on mute, not being available etc etc crashed into focus. And my senses were turned on. I think you must trust your senses. When I went to look there was stuff.
If I had said anything I would have been gaslighted, laughed at, side tracked. This also came later. Please don't say anything till you are happy or satisfied there is nothing to worry about.
It had been going on for a longish time and as I had no idea he was a bit casual. Receipts on the car floor. Coat pockets. Phone records. phone no's has he been calling. Face book searches ( there is a record) Looking where and how money has been spent, withdrawn. All things I had never taken the slightest bit of interest in or looked at. All texts and WA had been deleted on his phone.
I'm not tech savvy so there are other things I could have looked at that I didn't know about. I'm sure posters on here could tell you. Like location tracking etc that exists on phones. Google etc.
I found his Apple Id and linked his texts to our family I Pad and that's how I found out. I didn't even know this existed until the moment I did it. I watched their texts.
Don't say anything to your OH till you are happy. Hopefully you are wrong.