Hi. Thanks for asking in Healthcare Magic. Your symptoms of nausea, abdominal cramps and tiredness may be due to the high level of progesterone in the pill rather than pregnancy because severe abdominal pain in early stage of pregnancy is uncommon. Emergency pill or morning after pill is effective if it is taken within 72 hours after an unprotected sex. If the ovulation has already occurred then the morning after pill will not interfere with fertilization but will interfere with implantation of the fertilized ovum. Since you have got withdrawal bleeding, the chances of pregnancy is minimal. Although the failure rate is less than 10% you should still rule out pregnancy through blood test which is more accurate than the urine test. If found positive then you should consult your treating Dr. about further course of action. In future, if you don t want to conceive but want to be sexually active, then you should opt for a proper method of contraception like OCP. I hope this is useful to you.