Ineedabreak I sympathise a lot with your situation. I've been lurking on this thread and posted briefly with a link to my story a few days ago. I'm not sure if it has been mentioned already (I suspect it has) but you would really benefit from reading this book.
If you do decide ultimately that it is better to separate, please speak to Citizens Advice. As there are options out there to enable you both to live separately and you maybe eligible for a variety of benefits and help. It is well worth knowing where you stand legally and taking advantage of the first free session at a solicitors, they sound like big steps, but you do not need to commit to anything at all right now but knowing where you stand may bring you peace.
I took a stand with my H after excellent advice on my thread from WWIFN and others and I am glad that I did. I sent him a very long e-mail to outline what I required and thought I'd paste a snippet here for you:
"Your affair took a long time to heat up as it was a friendship that progressed over many years into a full fledged love affair. So I am no fool and realise that it will take time to cool down. I know you have been very ambivalent and that naturally you may have great difficulty cutting off all contact with her. You may also be reluctant to expose secrets and reveal continuing contact, however recovery of trust is greatly impaired by piecemeal staggered disclosure of basic information. You maybe putting off sharing everything with me as you think the truth will only make things worse. However the distress caused by sharing will be a short term reaction but the long term effect is that it will heal the wounds. I know you will not feel safe sharing in an atmosphere of nasty accusations and emotional storms and I will do my best to stay calm, but I actually need to hear how the affair began, how it ended, what was said, the lies you told etc. As if you keep giving me things piecemeal every time I think I have heard it all, I will be retraumatized with additional horror stories. Hearing the whole truth earlier in this process will help the recovery and give me more peace. I feel perhaps the reason you are not disclosing anything is a lingering loyalty to the OW and this is why you do not reveal details of the affair. I know letting go will take time, however for our marriage to have the best chance of surviving you do need to go cold turkey on contacting the OW as well.
I can no longer accept compromises and whatever crumbs you throw my way. Its not healthy for me or our children due to the underlying tensions and open conflict. You may prefer to put the topic of the affair in a locked box - but secrecy fuels obsession, obsessive thoughts about the OW maybe intensified by refusing to discuss the affair. Sharing information about the affair will allow us both to let go. Until I take steps to grapple with shattered assumptions and construct a story about the affair that make sense to me, I will be prone to obsessing until healing is complete. I am sure I will discover elaborate and premeditated and hurtful deceptions when the truth is uncovered, as long as you can validate the facts and empathise with the pain caused, I am hoping if we handle this together we will come out of it stronger."
I cannot emphasise enough that your H needs to be completely honest with you and fully transparent. He needs to stop all contact with her and change jobs for you both to have any chance of success at healing your marriage. I do not say this lightly. It sounds a little like you are still in shock and denial. Please listen to people like WWIFN. He cannot have his cake and eat it. You deserve more than that and so do the DCs.
After my H read my very long e-mail we had a heart to heart after he wriggled like a worm on a hook for a while and the truth was he never had ended the affair and had been lying to me. Whatever your H is doing in your situation you still need transparency and honesty from him and you need boundaries so that you can build up trust again in your marriage. I value marriage and I do not take it lightly but it is important that your children see you being treated with love and respect and are brought up in a healthy environment. They can pick up on underlying tensions. Mine certainly did and were far more at peace once my H moved in with his parents to give us space for a while. Seek outside help, look into marriage counseling, read that book, it is very good but do not settle for anything but honesty and transparency here and ensure he provides proof where necessary. Your marriage will never heal without these. I am not as articulate as WWIFN or others but I feel very passionately about this after everything I went through with my H. You deserve honesty and transparency and it will help you heal and move on. Generally the rule of thumb is to wait 3 months before making big decisions after the disclosure of an affair. Please also bear in mind that H's can do a lot of blaming of us in the early days for the affair, as they've spent so long justifying in their minds why it's ok to have an affair. Please do not accept responsibility for this affair in any shape or form. They can do a lot of re-writing of history, do not accept any blame here. Yes marriages go through bad patches and it takes two to make a marriage work but he could have sat you down at anytime and talked to you about any issues, not jump into bed with another woman. You didn't cause the affair.
Also please speak to your GP if you feel extremely low at this time. They can refer you for some counseling or prescribe anti depressants if needed. I didn't go on ADs until a whole year after separation as I didn't feel I needed them to begin with. But then I moved into this place of greyness, hopelessness, exhaustion etc and realised I needed to see my GP. Please speak to them if you start to find yourself descending into this sort of place.
I have two very young children so I may not be able to come on here much, or keep up with this thread very well, but you're getting some excellenmt advice from others, please pm me if you want. Sending you very unmumsnetty ((Hugs)) this is very very hard, but please take on board what people are saying x