I Started Taking Viorele, A Type Of Oral Contraception, In

I started taking Viorele, a type of oral contraception, in August, I started my pills the day I started my period and was on them for 2-3 months. Recently I was off of them for a month and started back up on November 1 when I wasn't on my period. I started my period November 25 and on the last day of my period (which was also my last pill) which was last night, I had unprotected sex. (And I was drinking before) What are my chances of being pregnant? Was the pill effective at this time?