Hi Doctor How Are You.. I Am Currently On Medication

Hi doctor how are you.. I am currently on medication for gonhorea. My period comes while i was on medication.it even comes before the due date with lots and lots of blood clot right through..just now when i pee and wipe with the tissue i see a string of blood on the tissue. I have had unprotected sex i take pregnancy test but its negative.what maybe the cause of the string of blood. My period ends over a week ago. Thanks you for your response