I too have UMS. It has actually ended a couple relationships in my past. It really isn't funny in real life, but I'm definitely going to have to use your term for it because it gives me a bit of a giggle.

I personally have always thought it was because my hormones have been and always will be screwed up. I never went further into it than that because there were always bigger fish to fry, so to speak. If you find out more please let us know.