Can I get pregnant right before my period?
The short answer to this question is no, you cannot get pregnant right before your period. However, the long answer is a little more complex. You can't get pregnant within a week of your period. However, your period has to be a true period in order for this answer to hold true.
There are many kinds of uterine bleeding, and a period is only one of them. The definition of a true period is that it follows an "ovulatory event," meaning an egg was released from the ovary approximately 14 days earlier. An egg is only viable for 12-24 hours after ovulation, at which time the egg will disintegrate in the fallopian tubes and be reabsorbed by the body. This means conception can no longer occur during the current cycle and must wait until the next ovulatory cycle.
Occasionally people experience bleeding at other times of the cycle that may be confused with a period. For example, because of the rapid change of hormones around the time of ovulation, some people experience light bleeding at this time of their cycle. Since sperm can survive in healthy fertile cervical mucus for up to five days, this is a very fertile time and thus could most definitely lead to a pregnancy.
Bleeding can also happen during implantation of an embryo in the uterus, so this would mean conception would have occurred a few days (3-7) prior to bleeding, however that bleed would not be considered a menstrual period.
Lastly, bleeding can occur due to a drop in hormones, without ovulation having taken place. This is called an anovulatory bleed. In this case, it would not be a true period, but could not result in a pregnancy because there was no egg released.
To know if you have indeed ovulated, and when you should expect a period, you need to be tracking your cycles using a fertility awareness method. The most reliable method is generally considered to be the symptothermal method (STM) where daily observations of your cervical mucus and basal body temperature (BBT) provide information that would confirm the presence or absence of ovulation.
If you are trying to avoid pregnancy, you will want to get professional support to learn how to track your cycles for the purposes of contraception. If you are trying to achieve pregnancy, you should be timing intercourse or insemination for your days of highest quality cervical mucus, a skill that can be learned through books, online resources, or work with a professional Fertility Awareness Educator.