Want to conceive after BC

Kate
Had our first in February of 2015 and ready for our next! Had regular periods for a while after him then suddenly two weeks on two weeks off period so I went on birth control about a month and half ago to regulate myself. Was planning to stop after this pack because of a vacation but the vacation just got cancelled due to weather. Can I stop mid pack and get pregnant quickly or should I finish pack? I'm at end of week two in this pack.