The shortest distance between 2 points is a straight line, you should get in the habit of setting goals/objectives for yourself everyday, it can be small things/big things, etc.
Confront your wife with the items I've mentioned, practice it a few times (actually more than a few).
Now the part that alot of people fumble on is the discussion that invariably follows after making these types of statements.
I have an easy solution for that as well:
"You heard what I said, that's all I really needed to say, I'm not discussing this anymore with you - I have made a decision on this and I'm good with it. Snap out of your funk, work on the marriage or work on packing your things & moving out - you won't be living here if you plan on having affairs with other men."
And then.... turn your back & walk away. If you have to leave the house, come back late at night.
You won't have this argument with her, trust me, it would be the wrong thing to do and you don't want to learn the hard way. She would turn this around and make you the bad guy & guilty for even starting this discussion.
If she mentions things like divorce, legal issues, custody, etc.
I'm living in the house until we're divorced if that's what happens, if you have an affair, you can be sure you'll be living elsewhere. As far as the children, I'm going for joint custody and I'll get it, I've already spoken with a lawyer. Anymore legal mumbo jumbo, have your lawyer speak to mine. That's my decision - THANK YOU!!!
You'll see that I've added "making a decision", "it's my decision", "I've made a decision", all these indicate taking back control of your life and your existing environment, don't discount it's use the way I've laid it out, saying it the way I've indicated will have a strong effect. You see up until now, the way she's acting, her leaving the marriage, her wanting to separate & divorce, her having affairs (EA or PA or both), those have all been her decisions, she made them without caring about your input. You're making decisions now, for you and you're caring about her input. She'll see that. It's a requirement, you will need to do this.
No specifics, again like I said just walk away, go to another room in the house, leave the house, go to a friends, just leave the environment.
The idea behind this is simple, you're aren't going to put up with her crap behavior anymore, you respect yourself enough to let go of the people who don't value you or the relationship they have with you. You leaving the room, the house, that environment and doing it regularly when you have a heated argument with her on this issue is going to show her that you are ready to leave her. She may not feel it at first but you do this a few times and the effect will be felt.