Birth control

Alrighty. So I have recently discovered that birth control works by stopping ovulation and with perfect use, meaning the pill is taken at the same time every day, the failure rate is less that 1%. If it stops ovulation, why do I still get change in discharge and pms symptoms such as really swollen breasts and bloating? Also, it protects against pregnancy, so paired with the withdrawal method is it safe if you're in a committed, monogamous relationship?