Re: Natural birth control
I used cervical changes for 19 years with no unplanned pregnancies (we have 4 planned children), then I had my tubes tied. It is by far the easiest natural method and is very accurate, but it involves feeling your cervix with your fingers, which some women may not want to do, but charting every day for years is a drag, and charting isn't as reliable as checking your cervix, because other things can affect your temperature besides your cycle. It will work for women with irregular periods but they may have to check for more cycles before they are sure they understand the changes. We used a condom during my fertile periods and nothing when I wasn't fertile.
I charted my temperature for several months at the start, along with checking my cervix, starting several months before the wedding, to help me understand the changes in the cycle, but after that I could tell when I was fertile with only checking my cervix. The cervix doesn't have to be checked every day once you are really good at understanding the changes, only when you are going to have sex. I always used two fingers to gently squeeze the mucous out, if there was any, to see if the mucous was clear and formed a sort of web between my fingers when I made a V with them in addition to feeling for softness, etc. I can't remember the name of the book we used to learn about this, it was 27 years ago. Any day where it was at all questionable we used a condom.
I have talked with a number of people who have gotten pregnant trying to use natural family planning, but they all did it wrong and didn't seem very serious about finding out how to do it right. One friend of mine who got married about the same time as me decided that she didn't need to read the book on natural family planning until the honeymoon! By the time she finished the book she was already pregnant with twins.