If you are wanting to find out when you ov thats trying.
ntnp is doing nothing at all.
You could use something like mymonthlycycles, you put your first day of your period in and it works out how long your cycles in and it tells you when your are due to ov.
Oh
Guess we'll be 'trying' then even though we wont be BDing when I'm OV
I don't think finding out when you are ovulating is necessarily TTC. Many people who practise natural conception methods do it to avoid pregnancy! I think it is a good idea to chart a few months before. This way you could give yourself the best chance of quickly conceiving when the time is right for you. In fact, I have been considering using OPKs for a few months before TTC (we haven't actually decided when to yet) to see if my cycle was back on track after having Tristan and breastfeeding as, at the moment, my cycle is a bit longer than before.
I think how long you chart for before TTC will depend on how regular you think your cycles are. If you are fairly regular, probably a few months would be fine - but if you are irregular, maybe using OPKS are the way to go. Before having Tristan, my cycles were always 29 days long and the three times I used OPKs, showed that I ovulated at around day15 - which would have been consistent with ov pains and so on.
Good luck! I hope you get a speedy BFP when the time is right for you.