Welcome to HCM,
You should have started birth control pill on a proper day. The first pill should be taken on first day of menstrual period. Bleeding during menstrual period contains fresh blood & clots, while implantation
bleeding is very light (Pinkish/Brownish). Thus your first bleeding might not be due to your periods. As you are continuously bleeding for more than a week, you should consult a Gynecologist in person for examination & investigation.
Wish you good health,