Birth control pills are an effective form of contraception. They usually come in a round pack or a rectangular pack, and it's up to you, the user, to make sure that you take the pills on a consistent basis in order for them to be effective.
Unfortunately, all forms of birth control have side effects, and most of these side effects will improve if you continue to take the pill over a period of time. You may experience some headaches, some nausea, and some breakthrough bleeding when you're using this form of birth control. If you experience any side effects regarding blood clot formation, such as chest pain, leg swelling, leg pain, headaches that don't go away with Tylenol, any visual disturbances, although these side effects are extremely rare, they do happen to some patients. You should stop the birth control when you experience those side effects and call your doctor. Let me reiterate. Those side effects are extremely rare, and while the headaches and the breakthrough bleeding and the nausea are annoying, they will usually get better if you continue to take the pills consistently over two or three packs of birth control.