Pardon me for interrupting.
I used a cheaper and supposedly more accurate way of monitoring fertility - by using basal temp.
U just need a good thermometer. Everynight place it near your bed before you go to zzz. When u wake up, the first thing u do (even before you sit up fr bed), is to take your temp. That is your basal temp. plot a chart and monitor the rise and drop in temp. When there is a slight rise in temp, it means that that day will be your ovulation day and it's time to have THE activity. The temp will remain high for few days. If it din drop and continued to remain high, congrats, you are preg! if it drop back to the normal temp, means the cycle is not viable.
This method has proven to work quite well. So, no harm trying