You probably have already, just didn't know it.  I was banging this chick from El Salvador a few years ago.  Stayed the night at her apartment; in the morning she was taking a shower and i was making coffee.  Right on top of her dining room table was a stack of mail; the top item was an already opened medical results panel from a STD test.  Positive for chlamydia, they had given her a shot to treat it.  

I'd been raw dogging her for a couple weeks.  I got checked and i was good, but damn that's crazy not to say something to me.