Spotting off and on for 6 days now.

I started spitting a week before my period is due. This is the 6th day it has happened. It's never heavy, but light. It doesn't happen through out the day. I don't need to wear a tampon or a panty liner, and most of my day and night it's stopped... Till the next day. It comes at random times as well, so not the same time. My period is due tomorrow. What might this be?