Is Pregnancy Possible Despite Taking Levonelle After Intercourse?

Hi - I took Levonelle 1500 just over a week ago around 10 hours after intercourse. My period is due in one week. I have been reading that levonelle is less effective if ovulation has already taken place, is this the case? I think I ovulated or started ovulating around 3-4 days before intercourse as I was cramping a lot. I also regret taking the pill and it is getting me down.