Just something that told you there was nooooo future?
I was seeing a chap quite some years ago, pre DH. We had been dating about a year, and were getting into bed at his place when I mentioned that I had my period, just in a casual 'so no rumpy-pumpy tonight' kind of way. The issue had never come up before.
He went all pale with disgust, said 'I wish you hadn't told me that', and proceeded to sleep on the floor.
Utter, utter twunt, I never returned his calls after that. Lucky escape.