Hi 1foot2, weekends are the worst, aren't they? I'm sorry that you are in the midst of an "epic funk", and rightfully so.
Try and focus on yourself tomorrow. Treat yourself (hopefully to something healthier than ice cream) to something special / different. And try and get yourself thinking of anything else than W.
Read Sandi's advice about LBH and the ineffective way we try and be nice to the cheating wife. She is a gold mine. W cannot respect a H who condones her cheating behavior by being nice to her. You may want to draw the line and stop being a "doormat" to her. But W still lives with you, and so take time to think about what is working and what is not working. Good luck.
