Well, I used the birth control pill as my ONLY means of contraception for almost 30 years, from the time I was in my early 20's. . In all those years, I never got pregnant and I never had an occasion to even suspect that I might be pregnant. Of course, I never "forgot" to take a pill either.
When you're on the birth control pill and you take it as you're supposed to, it's practically impossible to get pregnant. The pill prevents ovulation from ever happening. Because you never ovulate, you can't get pregnant. The pill is 99.9% effective, and that's about as close to perfect as you're going to get..