Condoms are very effective in preventing pregnancy if you have it on the whole time you have sex (meaning no genital rubbing without a condim) and it does not break. Emergency contraception is useful if you have an accident or the condom breaks. if your periods are regular and you feel healthy it is OK to use condoms as your primary form of birth control without a backup. If you want to be more secure, hormonal methods like birth control pills that you take every day are more effective than condoms, and can be used alone without a backup method. I hope this advice was helpful and good luck!