What Is Causing Brown Discharge And Cramping?

I have been taking Yaz (and then switched to generic) for about 2 years now. I last had intercourse mid-december. I got my normal menstrual the first week of jan. Yesterday. when I wiped myself after urinating, I noticed a slight brown discharge. Today I noticed the same as well. I took a pregnancy test and it was negative. I also have very lil cramping. Should I be concerned?