I have heard that as well - I don't have any experience with the fertility monitors so I can only let you know about OPK's. I think fertility monitors are around 200 bucks and you still need to buy the testing strips each
month. The most recommended type of OPK are the digital onces by Clearblue Easy since you either get a smiley face or a circle - but I have heard that many people get can get a false positive or a false negative. You can buy these at any
Target, CVS etc. They are near the pregnancy tests and cost about 30 bucks for 20 tests.
The only real positive way to know if you have ovluated is do have the cycle day 21 progesterone blood test which will confirm it. I forget, are you on Clomid? I think you said you were...I have heard that some women ovulate after CD
20, but from what my doctor told me if I ovulate after CD 20, Clomid is not working properly for me.
HTH! :)