I assume youre doing something so you dont get pregnant, right?

Okay then. Just be considerate and tell her ahead of time that you wont be home that night, or that you WILL be home for supper or whatever. No discussion about it, just put a calendar in the kitchen and say heres my schedule, now everybody knows. Personally it drives me crazy to have to report to somebody about when i'll be home - like im going grocery shopping and to the library - i'll be back tonight, i really doubt im getting kidnapped. But then im old and crabby.