That's a better idea...I'd go gor OPK's over CM anyday.
Have you tried ovualtion predictor kit yet? When you ge a positive it means that you "should" ovualte in the next 24-36 hours, which gives you time to bd. I think its a great way to know when you're ovualting
Hope this helps
http://www.fertilityfriend.com/Faqs/Typical-cervical-fluid-pattern-.html