Strange spotting episode, now late

So hubby and I made love during my fertile phase in September, and I should note we are using the pull out method. Then about a week later (after a night of drinking) when I woke up to pee in the morning I had wiped fresh red blood. None in the toilet. I thought, ok, here comes my period early because I drank too much last night and took an aspirin (both thin your blood out if I'm not mistaken) and then that was it. Nothing else. My period was due yesterday and has not yet come. (Bleeding episode was 4 days ago) I do not have the usual cramping or sore breasts that I do with my period. Just the back pain and the bad attitude ? anybody have any clue what's up?