I've been taking Dianette contraceptive pill for 4 months now. My periods have always been fairly light as I have PCOS, but since taking Dianette they've changed. Instead of getting red blood there's just a load of stringy black stuff which doesn't smell good. I used to get a little bit of that on the last day of my period, but now it's instead of a period. I thought black meant old blood, but I'm having a period every month so can't understand why anything would be building up long enough for it to be black.
Is this normal on BC pills?