Sorry to hear your AF is so late and you aren't UTD that happened to me a few times especially when I was coming off the pill (March07) I had some very strange cycles as my body was regulating again. It's regulated now however AF was 5 days late just the other day! That was annoying Have you just come off contraception?

Once your AF shows up, cd1 then you will just go from that and should ovulate approx 2 weeks after that.... as for iiregular AF's, if you are concerned I would see a Dr to get it checked out if you find it is happening a bit.... otherwise if you are stressed it could be stress related? Good luck I hope you get your BFP very soon! (with me!)