What Could Cause Delayed Periods With History Of Taking Levonelle?

Hiya, I took levonelle about 3 weeks ago, I had breakthrough a couple of days later for about 5 or 6 days. everything seemed fine but I expected my period yesterday and it hasn't come yet. Also my boyfriend didn't ejaculate inside me and I took the morning after pill within 10 hours. What are my chances of being pregnant?