Hi, and thanks for your question. It is great that you are being careful about your contraception
. I recommend that you discuss your question more in depth with your primary care doctor
or OB/GYN. Generally speaking, you only have to use a back up method for the first seven days the first time you start the pill. If you have already been on the pill for many months, you do not need to use a back-up form of contraception during the first 7 days of your new monthly pack. The reason that you are told to use a back up method, when you are first starting pills is because of the way the pill works. The pill contains a low dose of estrogen and progesterone, two of the female hormones in our bodies. In a woman who isn't taking any pills, these two hormones fluctuate throughout the months to make you produce a mature egg and make the egg be released from your ovaries and travel down in to your uterus where it can meet sperm and be fertilized to become an embryo and eventually a baby. The pill has small doses of estrogen and progesterone all the time, so that there aren't big dips or peaks that cause the egg to leave the ovary and travel in to the uterus (ovulation is the technical term for it). So, when you are first starting the pill, it is possible that the egg has already been released, since it takes some times for the pills to work and thats why you are recommended to use a back up method. Of course, unless both you and your partner have been tested for sexually transmitted infections, I highly recommend that you use condoms in order to prevent infections. Also, if you have any questions or concerns or worries that you may be pregnant or are having problems with your pill, visit your primary care or OB/GYN doctor.