Angel- I was in your shoes, and I didnt get 'proof'. I did see photos of women- about 5 on four occasions over a nearly six year period. He just explained them away. He also did what your h did, which was to change his passwords, deny he had etc. eg he would agree not to do so, then change the first letter into a capital one or some other sneaky strategy.You simply cant pin down a man like this.
I should have done what I did in the end- which was as follows:
- the usual, confront him
- listen to his denials
3 go away and worry like buggery that I may be wrong even through I sort of knew it all did just not add up, and then.......(and here is the different bit)
4 this time, I went back and said I had thought it all through yet again, and I still wasnt happy. There was too much tiny stuff, too many coincidences, too much general obfuscation and deceit. Fundamentally, I dont believe you.
5 Move into the spare bedroom and declare war
6 Listen to him tell our kids I was mad, and tell me I had invented all this because I had nothing else i my life etc etc. That bit hurt, and was truly shitty of him, because my work had dried up at that time, and I was very worried and sad by it, and had spent many years supporting him to get a career.
7 Eventually we went to Relate. He was hoping it would all blow over, and that I would move on from that particular focus when there. I didnt- I said I thought he was unfaithful and lying to me, heard is denial, and allowed the conversation to go in other directions for a few weeks. BUT, whenever the counsellor came back to me, even after some general improvements in the relationship, I said that I could not or would not move forward unless he talked to me honestly about my suspicions.
8 A week or two later, he backed down, and then I discovered there had been hundreds, and way less than half his age.
Angel, you know already, dont you, you just know. It wont ever go away, and there is no hope unless it comes out.
I so remember months and even a year passing where I 'let it go', but it always came back, the slight evidence grew, and he became shittier to live with all the time. It was a horrible time. Trust your instincts and escalate the finding out strategy however you can, or walk.