I took 3 active pills late in week 3 of ocella. had my period week, then started my pills like i do sunday. monday i had unprotected sex, and took plan b tuesday 15 hours later. and also kept taking ocella regularly. what are the chances i'm pregnant?

Impossible to say: the fact that you took plan b within the expected time course is a very good thing, however missing 3 pills makes your risk of pregnancy somewhat hard to predict. there is not much you can do at this point, but continue to take your pill, discuss the scenario with your partner, and consider birth control that you do not have to remember, like implants or IUDs.