...start days. Help? ? Like I said, I'm not on bc. I want to avoid having my period on April 4 because April 3rd is prom and I don't want to be pmsing and all broken out. I started my period february 5th (I'm on it now) my next period will be March 6th and the next will be April 4th. How can I change my cycle to where my period will be at least 2 weeks before or after prom? Can I start a pack of bc and not finish? If so, what day do I begin the pack and when do I quit?