There's a way of tracking your ovulation that is not that expensive, here's an example:

http://www.mts.net/~revive/cyclechk.html

I used it for several years, when I got older and the doctor got nervous about me still being on the pill. It works equally well for getting pregnant or for avoiding pregnancy.
It is the most accurate method to track your ovulation. If you are willing to check your saliva every day, it can work for you.