You should go to a doctor if that’s an option. Please ask about your medication and have them explain what to look out for. Some side effects are normal, and others are more serious, and that may not be the best birth control option for you. Emergency contraception is hard on your body, especially if you’re young. You took a large dose of hormones designed to reset your menstrual cycle, and it sounds like it has worked. The timing seems a little off, but otherwise those are normal side effects outside of the extreme pain. There may be something else wrong or that may be part of a miscarriage. Again, please go see a doctor because there’s no way anyone here can take in to account your whole situation.