Discharge before expected period?

Hi girls hey, so my period is supposed to be making an appearance either today or tomorrow. (I'm a teenager so it kinda does it's own thing, usually switches the weeks it wants to come on) but today for some reason I noticed some pasty discharge. Uh what is thisss? Last month I engaged in genital rubbing but there was no cum and DEFINITELY not any insertion. Oh and 3 negative pregnancy tests (3 weeks, 4 weeks and 4 1/2 weeks after the incident)! My period came 6 days after that though (when it was expected). I'm just wondering what's going on in my body.