On the one hand, I can't even imagine having sex when I'm in POIS, until about day 5 or even 4, but I have the same problem in that I never really get out. The other day, I was near finishing my cycle when whammo, got a cold. Miserable. My wifey "wasn't available", and of course, as son as she was, my cold was just about finishing.
Right into day 1 again.
I hardly ever manage to have one or two days clean!!
So I know what you mean!