Here are the facts:

-My last period was January 19th
-Had unprotected sex between then and now
-On Feb 5th, I noticed spotting & later on started light bleeding
-The bleeding was heavier at times but then light again too
-It consisted of red blood and sometimes just light pink with some brown
-I've been like this for over 3 days now
-I'm due for my period Feb 12th
-I've NEVER ever gotten my period early before


What could this be? My cycles usually run 24 days.. I took a pregnancy test 2 days ago & it was negative but obviously since i haven't missed my period yet.. I don't know what this is. Someone please help!