You did not mention what type of pill you are on. Anyway, it is common sometimes for abnormal bleeding patterns to develop in contraceptive
usage but they usually appear in the initial months. You should have a routine check up with your doctor to assess your general condition as well as look for any underlying pathology. It is always advisable to keep in mind that blood disorders may rarely develop while on contraceptive usage. If it persists, you may need to change your pill. Please get further suggestions from your doctor. Take care.