You only track your temp when you first wake up and should be done, if you can, the same time everyday. If you do it through the day of course your going to get different readings because you're moving around, your heart is pumping more, you may be in a hotter area, etc. As far as your cervix it should be high, soft, and you should have EWCM. The cm will stretch between your fingers. I usually get this a couple days leading up to ovulation.
your luteal phase (which is normally 10-16 days) should be about the same each month regardless if AF is regular or not. After charting for a few months you should be able to figure out when you're ovulating.
Good luck.
even with irregular periods? mine are 44 days apart avg.
When your charting you are only to go by your temp first thing in the AM (before you even get out of bed) Your temp. will constantly change through out the day so no worries about it spiking to 98.8 at 4pm. As far as O day, charting won't tell you when you're ovulating but your temp will rise and stay high after you ovulated.
Check out this website
www.ovulation-calculator.com