Hello, I am 20 years old, non-smoker, and because of irregular periods and recently becoming sexually active with my fiancee, my doctor prescribed me the Tri Cyclen Lo Birth control pill . I started the pill today(immediately), because I have no idea when my next period will occur (irregularity). My fiancee and I are going away to Europe in 11 days, and I was wondering if the birth control will be effective by this time. Thank you so much for your help!!!