It has been 11 days since you had your period after taking birth control pills, and it is considered to be a drenching period due to a change in hormone levels. Contraceptives are mainly emergency contraceptives, short-acting contraceptives, and long-acting contraceptives, but all of them are estrogen-progestin combinations. The main principle is to inhibit follicle maturation through hormones, preventing the formation of fertilized eggs to achieve the purpose of fertilization, but the use of contraceptive pills may also change the body’s hormone levels, which in turn affects menstruation, resulting in menstrual dribbling. Normal menstruation is generally cyclical endometrial shedding and bleeding, if after taking the pill, the role of estrogen and progesterone occurring in the body, changing the original hormone levels, then it is possible to affect the endometrial shedding and bleeding, which will also affect the menstruation, resulting in menstruation has prolonged phenomenon. Prolonged menstruation may also be related to other gynecological diseases, if there is any discomfort during the period, please go to the regular hospital in a timely manner to clarify the cause of the cause of treatment, to avoid delaying the condition.