You need to remember that it's not possible to determine the reason for your infertility until you undergo tests to find out if your husband's sperm count is normal; if your fallopian tubes and uterus are normal; and if you are producing eggs. Only after undergoing these tests will your doctor be able to tell you why you are not conceiving.
Your fertile period is the time during which having sex could lead to a pregnancy. This is the 4-6 days prior to ovulation ( release of a mature egg from the ovary). Women normally ovulate 14 days prior to the date of the next menstrual period.
As long as the periods are regular, this means ovulation is occurring. Some normal women have menstrual cycle lengths of as long as 40 days.
Unlike many other parts of your lives, infertility may be beyond your control. Don't blame yourself if you are not getting pregnant - it's a medical problem which often needs appropriate medical treatment.
The right to have children is a fundamental right of every human being and a very basic biological urge. Just because a neighbour has too many children should not deprive the infertile couple of their right to have their own.