I wouldn't just stick to cd14. Remember me I didn't ovulate until cd21! No way!!! He is just relying on the educated guess that you will ovulate about 6 days after your last dose....
Definitely use opk's - this way you will know about when you ovulate. My obs told me to get jiggy with it from cd10 - man were were exhasted by cd21!
I basically did it most days from cd10 to cd23. It worked! I of course used opk's as well which is how I knew I hadn't ovulated until cd21.

Wallow for a while if you need to, but you are on the road to success I am sure!