If you use birth control correctly, taking it every day at roughly the same time of day, using back up when appropriate, like the first seven days (or the whole first cycle to be extra safe) and while on antibiotic therapy, it is very rare to become pregnant.
The pill keeps you from ovulating so if no egg is released, you wont get pregnant. If you are inconsistent in taking them, it increases chances of becoming pregnant because taking them irregularly can allow you to ovulate. You are fine! The Pill was designed so that women could enjoy a normal full sex life without worrying about pregnancy. The only reason for condoms after the initial waiting period (or while on antibiotics and for seven to 14 days after you finish them ) is to prevent STDs. If you are in a monogamous relationship, you dont need condoms unless you miss a pill or take antibiotics.