you might know where i'm going with this. my mouth was a bit vulnerable after being intimate with her, and then i brushed my teeth with a tainted toothbrush.
at my house, everybody puts their toothbrush in a cup to the right of the bathroom sink, if the cup is tipped over or knocked off the sink, it all falls into the wastebasket, or on the floor next to the toilet (which hasn't been cleaned in years). it happens fairly often.
i had been using that toothbrush the entire time i've been with this girl