I feel the pain in your posts. The pain from your husband's affair was bad enough, horrible enough. But now you're beating yourself because of how you're reacting to that affair and adding that pain to the mix.
Gwyn, you have to stop. You have to find a way to rise up from where you are and shed some of this pain, you have to make yourself less responsible for your own misery. I know you're strong or you wouldn't even be trying to save your M after what's happened. You don't feel strong now but your strength is there and you have to trust it. Don't accept yourself less than you are.
You need to find love and start filling your life with it. This board is an excellent resource but virtual love may not be enough for where you are right now. Can you get love from your daughter? Can you call her more, can you go live with her for awhile, can she come stay with you for a weekend, what might work? What other relatives and friends can you go to for support? Lean on everybody available to you; this is your turn to be supported, you can return the favor when you've come out the other side.
If you can manage it at all find a good therapist ASAP. Then be piercingly forthright with them about your entire situation. Sometimes just talking to somebody helps the most and sometimes therapy can really open your mind to how your life can be. Make an appointment and go.
If you don't have enough real people available, find a way to God. I'm most familiar with the Christian version of God but explore any incarnation that gives you love. Go talk to a priest or a pastor or a minister or a rabbi. And if that person doesn't help you feel the love of God then go find another. I don't know if you're religious already, but if you become a Christian for only a month or a week or a day and it gets you over this hump then I don't care. Do it.
You have to work on yourself and accept help from everybody and anybody until your strength of mind is restored and evident to you. Then you can make yourself and others happy.
If you absolutely can't do that without separating from your husband or even divorcing him then that's what you have to do. I hope it doesn't come to that. But you have to put your focus on yourself right now and work on your marriage when you have some strength left over. No one will think any less of you for taking care of yourself. In fact, that's what everybody *wants* you to do.
Good luck! I'll pray for you and you know that everybody on these boards is pulling for you. Close your eyes for a minute and feel it. Then immediately start taking positive steps in your life. Don't wait!
Stop WaitingFeel EverythingLove AchinglyGive ImpeccablyLet Go