I was about to suggest internet cheapies but you are all over it already :)

I was using an iPhone cycle tracker trying to avoid falling pregnant. Second cycle, thought I had ovulated a week earlier so was safe, but no... Damn it! Of course I am happy to be pregnant, but the timing wasn't great.

That said, I know what you mean with how do people do it month after month... I'm lucky I've never had drawn out periods of TTC!

Good luck :)