Spotting before period!! Need advise!!

I'm 25 years old and have been on Diane -35 for the past 5 years, since I was diagnosed with PCOS.
Since Sunday I've been spotting and I don't know why!! Never happened before.... I'm not supposed to get my period until next weekend.
I took a pregnancy test and it was negative. Does anyone know what is going on with me?? :-(

Thanks!