sugar pills

exactly a week ago my boyfriend and i had sex and this was my first time. im on birth control and we used a condom, yet when we finished he pulled out and the condom was half way off. i've been freaking out and i've had many side affects of birth control, and pre period. i took a plan b after we did it and i'm just starting my sugar pills. could i be pregnant? and how long until i will get my period?