Ha ! I sympathise ! been there, done that twice (though the second was a partner not a husband !) first one was a compulsive gambler, second one a womaniser ..... the key is preparation preparation, preparation ! Luckily I was working for a divorce lawyer at the time the first one left .... My first advice would be : don't rock the boat ....quietly prepare by saving as much as you can without arousing suspicion (if you have a joint account) ......looking round to see what options you have if you decide to end the marriage ..see a good divorce lawyer for first preparative steps to see your legal entitlement, i.e. as regards the house, his pension, any insurance policies or investments he has (If you can, if you don't know, find out as much as possible !) .....this will put your mind at rest that a move on is, if you decide on it, possible. If he if fit and healthy the prospect of any money from the sale of the house being required for care might not be an element (or someone may say it was intentional disposal !) Open a separate account at a different bank, or, if you cannot find a bank to open an account with, the Post Office is always an option ..and you can opt to have your pension/s paid into that account as well. If you have any other income of your own, i.e. annuity, investments, etc find out if they are safe from the declaration of assets as you will have a reduced standard of living if you leave.
Assess your situation. If you are quite happy for it to continue as it is, then I would sit tight, save, ask for advice and play the waiting game if you can bear it ! Meanwhile, try to find out where he is going - hire a private detective just for your own knowledge if you don't want to divorce ...at least you will know ! Once you have found out who the 'other woman' is it is for you to decide whether to try to get to know her ....or to let her know you know about liaisons with your husband ...or just keep the info and evidence for future reference .....
You can turn your life around .....my present husband is now 83 and I am 69 this year ...he now has vasculaire dementia, in the early stages, and is often very aggressive and difficult to live with. There have been terrible times when I have wanted to leave but would feel guilty ! I just used most of my secret savings to refurbish the house - new kitchen, central heating, etc so now have to start again .....which I already have ! Trouble is, how much time have I got ? who knows ! should I spend it feeling that I would rather not be here with him, or feel guilty and go ? ...decisions !