luteal phase. That is the time in between ovulation and the next menstrual cycle. It should be between 12-16 days. So if you know what your LP is normally then regardless of whether you ovulate late or early you can guesstimate when you should expect AF.
well I dont think I o'd last month ,thats the problem..I was under alot of stress and it made my body out of wack....I o'd this month though on the 26th.
maybe you ovulated later than you thought in that last cycle. If you know when you ovulated and know your normal luteal then you should be able to calculate when you would expect AF a little better. Hope that helps.