Hello, Following the use of the post-coital emergency contraceptive pill, your period might be different. Most women will have a normal period at the expected time, but some may have their period later or earlier than normal. If your period is more than 5 days late you should contact your doctor as soon as possible. Since your pregnancy test is negative then other following causes of the delayed period should be ruled out by relevant lab tests by your doctor like 1. Emotional stress or physical illness 2. Hormonal disorders like thyroid disease, high levels of Prolactin, 3. Inadequate diet, change of job, etc. 4. Extreme physical activity 5. Diseases of the ovary like polycystic ovarian syndrome, etcetera. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali