I started taking my birth control on the first day of my period. i started february 10th. unprotected sex no pull out last night. chance of pregnancy?

Very little: You do not need a back up method of birth control when starting pills on the first day of your cycle. Birth control pills are 99% effective with "perfect use" (never missing a pill and taking them the same time every day), but about 91% effective with "typical use" (using them the way people typically do - occasionally missing a pill, not always taking them at the same time each day, etc).