I heard birth control can be used as emergency contraception, so if i missed 3 pills(not in a row),will it act as a "plan b" and not allow pregnancy?

Higher dose: The hormones in one birth control pill are not in high enough levels to be used a an emergency contraceptive (EC) Multiple pills must be taken to get an emergency contraceptive effect. Your doctor can advise you on the number of pills needed, depending on the specific birth control pill. Missing a birth control pill increases pregnancy risk, so EC would be needed for each sexual encounter.