Birth control is over 99% effective when used perfectly. But taking doses late or missing doses brings down that efficacy. With "normal" use birth control is 91-92% effective. IT IS NOT PERFECT. There is no satisfaction guarantee (we wish!). How late you can take your pill and still be protected depends on the type of pill you are taking.
We recommend using condoms in addition to your birth control. Condoms are great for STI prevention, additional contraceptive protection, and the peace of mind associated with both of these things!