It could've been implantation bleeding depending on how heavy it was. usually it is light spotting (so ive heard, never had it myself) i know when i was ttc i had a couple of cycles that were off like that and of course i got my hopes up

. if it was implantation i think a positive would most likely show up in a couple of weeks, not right away. You could also see your doctor for a blood test in a week or so. good luck and i hope you get the answer you want! take care