If i lost my last week of birth control but had a extra pack of it and just continued with the birth control could i be pregneat?

Probably not: Assuming that you have been taking the pill regularly otherwise, without any missed pills, then the chance of pregnancy remains extremely low. With proper use of the pill, the chance of pregnancy is <5%. Many women take the pill "continuously" without a break for a period. Finish the current pill pack, allow for a period, and then restart as usual. Check a pregnancy test at some point!