So what are you doing to protect your finances, Oxford? You never really did say.
When my wife had her affair, I immediately had my paycheck deposited into a new account that I opened, that only I had access to. I let her know after I had done that, and that I would be transferring "$X" into our joint checking account to cover the family's monthly NEEDS, as well as a reasonable amount of the kids' wants. I also let her know that I had decided that I was NOT willing to help finance her affair, and so her hair coloring, VS undies, make-up, tummy-tuck monthly pmts. on her Visa card, and her cell phone bill -- were HER responsibility. I continued to pay for her basic needs (health insurance, gas, basic toiletries, BASIC clothing allowance etc).
I couldn't stop her from having an affair, but nowhere was it written that I had to financed the damned thing.