Hi,
i dont want you to freak out here but my doctor told me once that if you are late starting the pack you could ovulate during that time and that usually the first couple of days of the new pack are the most important because they tell your body to stop ovulating for that month and the rest of the months pills are there to keep up the message not to ovulate.
If you did have unprotected sex and its not to late I strongly suggest you get the morning after pill.
But then again, some girls dont get pregnant when they are off the pill for months, others get pregnant if they are a few hours late. Everyone is different.
Hope everything works out ok.