Just to make you feel better I looked @ your chart and thought you looked to have o'd on CD17 or CD 21 too, but not the greatest at working it out, then saw the posts by the other 2 ladies .
It may well take sev cycles for your body to settle down.
I know its slightly different, but still hormone related, I statrted charting when I'd had my 1st AF after having my DD which was ~ 12/12 ago. For sev months my cycle was all over the place, and I'd often ov late in cycle. Its only in the past 6/12 I'd say things had settled down , I can now say I normally o around day 15/16.
You may find fertility friend is a little better as it gives a coveline when you od is, but doesn't predict fertile days unless you have VIP membership.
You can also use fertilitycircle which does give you fertile days with standard membership.
|Each site uses diff method to calculate od. So you may find that if your temps are a bit erratic then you may get a different day.
We've been using natural family planning for past year.
Tend to use withdrawal from CD10 (just to be sure) until 2 DPO as per charts.
Hope this helps.