Tia-

Martin has given you the days that you are most likely to conceive. Ovulation occurs around day 14. You can neither get pregnant, nor make omelets, without eggs.

I highly suspect that Martin meant to say to abstain from day 8 to day 20 of your cycle.

The failure rate for this method of birth control is 25%. If you had a one in four chance of winning the lottery, you would have a purse full of tickets, wouldn't you?

Oh, the word infertile as shown of the diagram is relative, not absolute.

JayR