Rachael said:You work 14 days back from AF for a rough idea, that is assuming your Leautal Phase is infact 14 days.
If you do this as a guide, start watching for fertile signs such as increased CM, egg white CM around Day 11 of your Cycle.
After a few cycles of paying attention to what your body is doing,you will have a better idea of when you actually ovulate and how long your Leutal Phase is.