7 days back i had taken an emergency pill unwanted 72 after an unprotected sex i had my periods ended just a day before the act. now it's bleeding

Emergency contracept: Emergency contraception causes irregular bleeding. This is normal but is not a normal period. It is hard to say when your next period will occur. The emergency contraceptives need to be taken within 72 hours after sex and waiting 72 hours is pushing the envelop of its effectiveness. I'd suggest a pregnancy test in 3 weeks to be sure as well as starting a reliable method of contraception.