Welcome to HealthcareMagic. It looks like breakthrough bleeding
but you have not mentioned when did you start your contraceptives and whether you had unprotected intercourse
before starting contraceptives. If you had unprotected intercourse then chances of it being implantation
bleeding are there. But if the answer is no then it is breakthrough bleeding due to contraceptive pills. It is normal for this kind of bleeding to be brown in color and can last for several days.
Hope it helps you. Regards.