Got a chuckle out of the shirt idea. I have my doubts that you will actually do it though....but it is fun to think about, isn't it? LOL
Okay, more importantly, STOP that damn backsliding! You are making it worse for both of you. Instead of the accusing words (and they do sound accusing) try something like, "man, oh man, all of the sudden I feel insecure H. Give me a minute and I will be fine." Then breathe and GET OVER IT. Chances are he will say something to help the situation. I mean it Deb...CUT IT OUT.
And yes, I can see that OW is a manipulative wh#re. She is probably eating ice cream like a fiend in order to get the desired effect. LOL There is likely more to come on that front. Prepare yourself and don't fall apart. You can do this.