I am on my first second pack, 3rd week of the Sprintec birth control. I decided not to take my white inactive pills from my first pack. I didn't take about 3 of them before I actually was able to pick up my prescription and start my active pills at my regular time. My period came on maybe 2-3 days later and now it has been on for two weeks, versus being irregular not on birth control and having periods lasting between 4-5 days.