spotting? on birth control?

i started taking birth control about two weeks ago on the start of my period. since then my period had stopped, however i have been having mild cramps and gushes of blood here and there the past four days. prior to leaking fresh blood my discharge contained trace amounts of blood making it a slight pink, which the doctor told me was normal. but now its dark red or bright red fresh blood in pretty big amounts (enough to leak through pants) for spotting i believe. i am not sure what to do or what exactly is normal for beginning birth control and the spotting problem i have been facing.