Hello.. excuse nickname, it's my "name for discussing-DH's-past-beastly-behaviour" and I've signed in using it just to offer moral support to you both and any one else in this horrible situation.
No real gems of wisdom to offer, just to say, as someone said below, you CAN get past this, but he has to understand what he needs to do in order to make this possible. I think you (unfortunately) have to live with the risk of relapses but it does get better and easier. It's not fair and it makes me very angry all over again when I read these threads. Who do they have to do it! WHY? It's all so unecessary and very very hurtful to the woman. It makes you doubt them in almost every way and suspect them of things that they later turn out to be completely innocent of, all because we have been forced to accept that they can lie through their teeth when they want to, just to cover up their own pathetic behaviour. So how the hell are we to know when they are telling the truth??
I hope I have made it very clear to my DH now that I cannot and WILL not put up with any more of this kind of behaviour. For a while, existing in complete misery and not knowing how to get through the days, (after he had promised it would never happen again and I kept finding evidence that it had ) I tried to convince myself that maybe this was what I had to accept if I wanted to be with him.. "at least he's not actually shagging other women" type thing... (although you do of course live in fear that maybe he has or will even if this is/was never the case). But in the end I felt the whole situation was destroying me. I felt I was losing myself in a pit of misery and fear and the stress of trying to soldier on as normal, with no appetite and no zest for life whatsoever, was just too much. I thought "I can't do this.." and started to consider how we could separate (it would be straight forward in our case.) Strangely enough, HE grovelled to me around this time; I never even TOLD him I was considering asking him to leave.. (until recently!) I didn't threaten or beg as I had in the past, I was quietly getting from day to day, telling no-one (I found it difficult to confide in my best friend and she is HIS friend too and it made HER hate him and unable to 'deal with him' normally!) wishing the whole nightmare would disappear and trying to talk myself into a state where I could end my marriage to a man I really did and do love, have always wanted to spend m whole life with, the father of my children (and a good father at that!) and who is, essentially, a good man, despite everything.
He went to great pains to reassure me over and over again that I mean the world to him and that he does not want to lose me and the kids and that he is through with "all that" and doesn't want to keep making me ill with stress. This was a couple of months ago now. I want to believe him and I have felt better for weeks now. I am hoping this is something we can put behind us but so much damage has been done. A couple of weeks ago I said to him "I was considering us splitting up in December, I was planning a life without you." Hard to say if he believed me. I'd like to think I shocked him with that remark. It is true after all.
I think it is the sort of thing you could look back on, when you are both old and grey, and still together (!) and see it as a "blip".. after all, some people can and do put affairs behind them and manage to have a strong and happy marriage afterwards. So I live in hope that I, and all the other women on here in the same position (we crop up regularly I can assure you!) are actually with men who manage to get their acts together, stop thinking with their dicks (excuse me but this is what they ARE doing when they behave like this) and realise without any shadow of a doubt what they could have lost.
Thinking of you. Stay strong.