A very difficult situation. For which I have no answers. However you have to do what is best for you. What I have learnt through this process is to take some time out for yourself. To let the initial panic/frustration/horror pass, and to think of the longer term consequences of your confrontation. I am not saying don't do anything, but think carefully about what you say and how you say it.
Perhaps consider "acting" like a good husband. Go on a date. Remind her of how good you can be to her. do something fun, make her laugh. Give her something else to think about.
Others may disagree, I am just giving a little food for thought...
