Well Fisticuffs, it was all a bit predictable really. I found becoming a mum, stopping working and moving to a new area where we knew no one all at the same time left me feeling a bit lacking in identity. Like all I was was a mother and housewife. At the same time DH was totally preoccupied with work and really took me for granted. Sex life was zero as he wasn'nt interested. An old acquaintance from my working days got in touch with me - we'd always had a bit of a spark and we'd kissed once, but nothing else - and said he was coming down to my area and cld he visit? He turned up and the attraction was still there, so strong, and the way he was with me made me feel like a real woman again. Nothing really happened that day and he went away again but then we texted every day for ages and I engineered a situation where I cld meet him again some weeks later. It was all quite frantic by then, and things with my DH had gone from bad to worse - naturally, as all I was thinking about was this other fellow. Anyway when I finally did see him (he was single) we were both so consumed with guilt about the fact that I was married with a child that it was a total non-event. I came home feeling massively deflated - because I knew it was all over. I felt I had nothing with my DH, and that I would never feel desirable and sexy in my own right again, as I couldn't pursue something elsewhere.
After all that, DH read my mobile phone bill, put 2 and 2 together, and then the shit really hit the fan. We had a horrendous few weeks. It was ironic how vile DH was at times, since he himself had left his first wife for someone else (not me) and had always made a big deal of never judging other people who were unfaithful. I guess his own wife doing it was a little too close to home. Anyway, I decided that I didn't want to leave DH as I felt, like you, I couldn't break up our family for my own selfish reasons. I hoped that DH and I cld rebuild things.
ANyway that was over a year ago now and we are putting it all back together and I think it will be OK. But it does take time for the hurt (on both sides) to pass and I think in many ways what I did, though it forced us to look at our relationship, obscured the real issues between us, IYSWIM.
Must go, but do be careful you don't get caught if you are going to carry this on - I understand where you are now, but the pain all round will just be so horrible if your respective other halves get wind of your affair.