Gwyn- You're going to think about the A sometimes. In fact, you should. It was real for you, it happened, it hurt you. It never goes away. Maybe it will be helpful for you to think about the ways in which you will allow yourself to think about it. For instance if you're torturing yourself wondering about details, etc. maybe use thought stopping and try to move on with something else. But if you're just thinking about the progression of things, about the problems that led up to the A, about what may have been the important factors for H in having the A, about how he feels about the A now, etc. then I would say that those are thoughts you should allow yourself to have. You need to be good to yourself and nurture your wounded heart. These thoughts don't need to be communicated to H, they can be private. In fact, given H's determination not to speak of the A, these thoughts probably should be private, at least until your M gets back on solid ground. But they are yours and you can think them if you need to. You are still a separate person with your own feelings and needs.
"Happiness is a butterfly, which, when pursued, is always just beyond your grasp, but which, if you will sit down quietly, may alight upon you."