Whether or not you have a period each month doesn't necessarily mean you and or cannot become pregnant. If you have a period and don't have any problem (even a minor one) that will prevent becoming pregnant, then you get pregnant. You can, however, have what seems like even a perfect menstrual cycle and still have something wrong that prevents pregnancy.
Usually, couples are told not to be concerned about fertility problems unless they try to conceive for a year without succeeding. Even then, it doesn't necessarily mean there's a fertility problem.