It's an assumption that every women with 28 day cycles ovulates on cd 14. That's textbook perfect. I for one have 28 day cycles but ovulate on cd 12 or 13.
There is a great book out there called taking charge of your fertilty. It helps you understan the different signals your body gives off when you are most fertile. Cervical mucus, body temps..Etc.
Having sex every day of the month is just plain stressful and exhausting. As one response said...Sex every other day during your high fertility days is best.
Sperm can live for up to 72 two hours. If your cycles are 28 days long and you started having sex every other day from cd 9 through cd 15...You'd be really maximizing your chances for conception.
Hope this helps!
Nancy
edit