Description
The Sympto-Thermal method uses multiple natural family planning methods and requires you at the very least use the Basal Body Temperature and (Billings) Ovulation / Mucus methods. As you get better at this you can prevent pregnancy by observing your body's reactions which indicate its fertility (or use the reverse to try and get pregnant).
When you are not fertile you can enjoy spontaneity with sex and still have a low change of becoming pregnant.
Effectiveness
At best it is 98% effective, even when you are irregular or nursing because you observe your watch your body and can see when you have become fertile. Just make sure to cross check your reactions and observations from month to month to reduce inaccurate readings.
Directions
Your body temperature naturally goes up when you ovulate so you can check your temperature as your first indicator.
By observing mucus patterns during the course of your menstrual cycle you can see the changed in your cervical mucus, and can determine when you're least and most likely to conceive.
Drawbacks
You will need to see a family planning center or physician to learn this, and will need further home study in the form of books or course's.
