With a normal luteal phase the latest would be 11 days before the day you expect your period to start. If you have a luteal phase defect it could be any time up until you start your period. A luteal phase defect is when your luteal phase (time between ovuation and day 1 of next cycle) is shorter than 11 days. This is caused by a low progestrone level. It's pretty much impossible to substain a pregnancy with a luteal phase defect.
That being said you could be having a long follicular phase (the time between day 1 of your cycle and the day you ovulate) this month which somtimes happens. Usually it's realted to a recent illness, recently coming off of birth control, an illness, stress, and many other things but it can happen to pretty much anyone. Often women notice changes in their cycle during TTC and many believe it's because of the stress of TTC.
Just keep charting and see how things go.
at 7:50 PM on Nov. 28, 2010