Vaginal Discharge

Like most women, I usually get a white or clear discharge monthly before and after my period.  For the first time today the discharge was a mustardy yellow.  Some of ti was thick and some almost slimy, there was also a slight cheesy odor to it.  Should i be worried? I have had yeast infections in the past, but it has been over year since the last one.  I also have 2 very small cysts on my ovaries.  I am not sexually active so it cannot be a STD.  Please Help!!