Thank you for your question.
Emergency contraception is of two types. One is the oral tablet which you have used. The other is the copper IUD which can be inserted up to 5 days following unprotected intercourse. Your doctor will be able to guide you best on which one is most suitable for you.
In young fertile women there is no such thing as safe period. All unprotected intercourse poses a risk for pregnancy and sexually transmitted infections. If you are using the emergency contraceptive tablet you need to take it as soon as possible after the exposure, ideally within 24 hours. It can be taken up to 72 hours but the efficacy decreases the longer you leave it. You can use it again in the same cycle but not necessary if a repeat accident happens within 7 days.
please be aware that emergency contraception (other than the copper IUD) does not give ingoing protection against pregnancy and is not as good as regular effective contraception. If you find you are using emergency contraception more than 3-5 times a year you need to get better contraception on board.
Also remember that all sexually transmitted infections do not cause symptoms. If you feel you are at risk please see a doctor specialising in skin and DVD urgently for correct medication.
hope this clarifies things