The levonelle 2 pill, which i'm guessing you took, is only effective when ou take both pills twelve hours apart, if you forget it I don't know what the effects are, you can take it no more than 16 hours after the first though. If it has only been a day since you had unprotected sex or the condom split or whatever happened. Then go back to the doctors and get another perscription and this time remember both pills. If however it has been more than 72 hours, then I don't think the levonelle 2 pill will have worked and you need both doses of the hormone to stop the sperm settling in the egg. If the sperm does settle then one dose of the hormone has shown not to harm the developing foetus.