I have regular cycles, I always come on at the end of the month but never the same exact date. So how do I know if I'm late? This month was my first time tracking everything and logging my positive opk and glow said af should have started on the 27th but it didn't. But as I said I always come on at the end of the month but different dates so I have a another few days to come on yet. So what should I actually count as being late if I ever am?