Hello dear, The emergency birth control pills are considered effective when taken within 72 hours of unprotected sexual intercourse. These pills have high hormonal content. And since you have taken 4 pills accidentally, it can cause hormonal imbalance in the body, resulting in delay of periods. However, to relieve your apprehension, you can get a Pregnancy test done using a Pregnancy kit. In case of pregnancy, it will give positive result within one week. The reasons for delay in periods and spotting can be many such as hormonal imbalance(as already explained), anovulatory cycles, stress, any infection or pathology in the uterus, ovary, etc. So, if pregnancy test is negative & periods are further delayed, kindly consult a Gynecologist & get a proper clinical examination done. Investigations like complete blood count, Ultrasound scan of abdomen and pelvis will be helpful to rule out any pathological cause for your symptoms. Wishing you a good health. Take care.