Hi Chimpette--I know there have been ladies on here who have gotten pg even though they didn't get definitive opk + that cycle (Jessiecat and KileyJean). Do you normally get opk +?
The best way to know (on your own) if you are for sure ovulating is to take your basal body temp every morning. Not sure if you already do that. The upward shift in your temp will confirm that ovulation took place--it's after the fact, though, so not that helpful in predicting bd timing unless you end up with very regular cycle patterns. But it is useful if you are worrying about whether or not you are ovulating.
Good luck!