My body is used to this birth control, i always take the pill same time never miss aone. why could it be a week early with heavy clots?

Bcp bleeding?: Bleeding with clots is rarely observed on low dose bcp's. If despite regular use of oral bcp's, you have also not delayed starting a new pack more than seven days after taking the last active pill (i.e., no gaps after placebos are ended), this may be due to delays more than 24 hours after the preceding "active" pill. If pregnancy is possible, get a serum HCG test to be certain.