Hi, The morning-after pill, also known as emergency contraception, is a type of birth control that can be taken after unprotected sex to prevent pregnancy. It contains a high dose of synthetic hormones that prevent ovulation or fertilization of an egg or prevent a fertilized egg from implanting in the uterus. Some of the potential side effects of the morning-after pill include: - Nausea and vomiting - Headache - Dizziness - Fatigue - Abdominal pain or cramping - Breast tenderness - Irregular menstrual bleeding or spotting - Changes in menstrual flow or cycle - Mood changes It is important to note that the morning-after pill should not be used as a regular form of birth control, as it is less effective than other methods and can have more side effects. It is also not recommended to take the morning-after pill multiple times in a month, as it can disrupt your menstrual cycle and increase the risk of side effects. If you are experiencing cramps and back pain, it is important to speak with your healthcare provider to rule out any other potential causes. Additionally, missing your period for 5 weeks after taking the morning-after pill is not uncommon and can be a side effect of the medication. However, if you are concerned about pregnancy, it is recommended to take a pregnancy test and speak with your healthcare provider. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician