Yes. If ur on the placebo/break week of ur birth control, ur period can start anytime from the first day to the last day. If u got off the birth control completely, it can generally take 3-6 months for body/natural cycles to adjust, so irregularities are normal during that time. That said, if u got off the birth control completely & had unprotected sex, then pregnancy is definitely a possibility & u should take a test in 2-3 weeks.