Can the BC pill mess up period?

I just got on the BC pill 2weeks ago. for the past 3 month my pd have came on the 16....14....and 11. these are the 3 diff dates they started in the last 3 months. my thing is my pd hasnt came yet so is it possible for the BC pilll to hinder your period or wat and NO im not prego b/c i had to take a prego test b4 i got the prescription 2 get on BC