I agree with Lissie. The monitor is wonderful and I can't say enough great things about it.
It is costly ($200 for the monitor, $40.00 a month for test sticks) but well worth every penny.
Women can ovualte at anytime, but most ovualte around day 14-16. But according to the monitor, I found out I ovulated early on days 11-12. My sister-in-law also used the monitor and got pregnant her first month of using it. She found out she O'd on days 21-22.
You should give it a shot! It worked great for us.