How It Feels
Keeping a record of your menstrual cycle (fertility awareness) takes time and effort every day, but it is important to do so to find out your most fertile time.
You may have an unplanned pregnancy using fertility awareness. To use these methods to prevent a pregnancy, do not have sex during the entire time that an egg can be fertilized, including 5 days before ovulation.
Generally, your most fertile days begin 5 days before ovulation and end on the day of ovulation. Pregnancy can occasionally occur after ovulation, but it is less likely than in the days before ovulation.
Calendar (rhythm) method
If your menstrual cycle is 28 days long, you are most likely to ovulate about 14 to 15 days after menstrual bleeding begins.
If you do not want to become pregnant, the calendar method of birth control is not the best choice for women who have short, long, or irregular menstrual cycles. For this reason, the calendar method alone is never recommended for birth control. It must be used in combination with other birth control methods.
Standard days method (SDM)
The SDM works best for women who have cycles between 26 and 32 days long. If you have more than one cycle in one year that is shorter than 26 days or longer than 32 days, you need to use another method to avoid pregnancy.
Basal body temperature (BBT) method
Your basal body temperature (BBT) usually drops about 0.4°F (0.2°C) below your normal temperature 1 to 2 days before ovulation. It then increases the same amount or more above your normal temperature 1 to 2 days after ovulation and stays high until just before your menstrual period begins. Since the rise in BBT does not occur until after ovulation, it is possible to become pregnant if you have sex just before or during ovulation.
Many women do not have a regular temperature pattern, so it can be hard to use this method to know when ovulation occurs.
Cervical mucus method (Billings method)