Struggling with my situation

Hello everybody. I am new here, but so tormented I had to find somewhere where I can let it all out and hopefully get some good advice. I apologize if this post is a little long.
My husband and I have been together for 49 years and married for 47. When we had been married for just over 30 years, I was heading deep into the menopause with depression, insomnia, the works. I also had other underlying and undiagnosed health issues all contributing to the way I felt. Suddenly I felt worthless, past my use by date, no libido, felt that any good career opportunities had passed me by and I basically felt like a failure with no future. Then I got a computer. My husband and I slept apart because of my sleeping problems and the computer was in my bedroom. I absolutely loved chatting to people all over the world, but unfortunately I met up with a guy who started chatting me up. In my depressed state, this felt like just the boost I needed and I became infatuated with him. He asked me to write to him which I did. It seemed all very exciting, until my husband found the unposted letter. I stopped the relationship and stopped looking for trouble and went back to work. I can't even remember if we had a discussion about this, but I'm sure I must have said that I had ended it all. A while later because of the menopause, I could no longer be intimate with MH. I tried everything, but reacted badly so one day I simply had to tell him I could no longer sleep with him. He didn't seem too upset about it.
We carried on together, I thought in a good relationship, but without the sex. At one time I suggested we could just cuddle, but he said no, that would give him feelings. I felt rejected, but didn't push it. I can remember nights when I would cry my eyes out in my room, feeling so lonely for him, but I didn't say anything to him for fear of more rejection, although we seemed to have the same closeness that we had before, but without intimacy. I thought everything was fine.
Fast forward 15 years and MH is in a rest home with dementia. Sorting through his things, to my horror, I found a page of my email addresses he had copied down. I had these written on paper beside my computer. He must have done this all that time ago. Most of them I stopped using years ago. There was only one address that was suspect which related to the fling I had, but I never used it again after that and probably only used it a few times anyway. MH never understood computers and clearly assumed all of these aliases I had were to do with cheating. They were all perfectly innocent. I have always been a very private person and whenever I joined a new group or forum, I would create a new ID and email address. One was simply an address used to set up Skype so my best GF in Australia and I could talk for free. There was a man's name jotted down, again completely innocent, but instead of coming to me, he must have assumed I was cheating, because in amongst it all, was the name of a sex worker and her phone number.
Now I am so distraught, not only dealing with the grief of losing my husband to dementia, and with being alone without him, that I now have to struggle with this new information and the fact he was having physical contact with another woman. I love him to pieces, but my own health was so bad from other conditions these past 10 years, I still felt adrift, fatigued and depressed. Then these past few years I had the strain of his developing dementia and caring for him when I didn't feel so crash hot either. In some ways, I can forgive him if he was connecting with a prostitute, but if the reason was to get even with me, I feel so gutted that he got it all so wrong. What is perhaps even worse is that I have no chance of explaining it to him. He still recognizes me and tells me he loves me and misses me, and I say the same to him, and it's true, but otherwise he is a very confused old man, 10 years older than I am. I can barely live without him but I am left with this dreadful emotional pain which I don't know how to resolve. Perhaps over the years he forgot about it all anyway, with dementia taking a hold, but that doesn't really help me with the knowledge he felt he could no longer trust me. After that episode, I never got snared online at all again, and when I look back now, I am horrified that I could have done it, but I am in a way better state of health now than I was then and if I'd felt alright back then, it would never have happened in the first place.
I also feel pain over what I feel as lost years, but I don't expect anybody would ever understand my situation, dealing with the menopause and a B12 deficiency combined. It has taken me 8 years to work out what the best treatment for me is, but now that I'm fine, I have lost the opportunity to get closer to MH ever again.
Thank you for reading this, if you got this far.