What Causes Periods While On Birth Control Pills/

Hi, I have had many issues with my period for quite sometime now. My OBGYN has changed my pills a couple of times to try and get them straightend out. I am now on my period for the 5th day and still passing dark read blood clots and not to mention I am still in the middle of my pill pack so I shouldnt even be on my period. This is not the first time this has happend. I have had a period to last for 14 days. I have an appointment for my pap in a week but what should tell my OB that I need as far as any tests?