Contraceptive pills such as othro are not the same thing as plan-b or other "morning-after" pills.
Starting ortho
after unprotected sex will not prevent pregnancy. Ortho must be taken as a regiment
before unprotected sex.
If it is less than 72 hours since you had unprotected sex, then you can still go to a store and get plan-b or another "morning-after" type of pill.
Starting ortho right now isn't going to hurt you in any way. It won't hurt any part of your reproductive system, even if there is already a fertilized egg on its way to the uterus.
The reason ortho won't work like plan-b is because plan-b has higher doses and different horomones in it, and so it stops ovulation almost immediately, unlike ortho, which eases your body into the new cycle.