I Had My Period 8 Days Ago (which Was At

i had my period 8 days ago (which was at its normal time usually happens every 4 weeks like clockwork), it lasted about 4 days and was very light. Today I have cramping and am bleeding again. I did take the planned b pill a couple days before I had my period. I took a pregnancy test a couple days before my period and it came out negative. What does the bleeding mean?