Help please......................?

Ok I get my packs delivered to me and I get 3 months at a time. I was currently on my last week (the sugar pills) waiting for my pack to arrive in the mail. I was supposed to start my new pack of birth control the upcoming sunday, and my pills did not show up until Tuesday. I had sex on sunday and Monday morning..but I had gotten my period on Thursday and it stopped saturday morning. What are my chances of pregnancy? My period started again on Monday the whole day and then it was done. I usualy have it for like 4-5 days, but im not sure why I had it 2 days then it stopped for a day and then started again the following day?