TTC but OPK problems

Shannon
My partner and I have seen out fertility doc and everything has check out. We've ordered sperm and are just waiting for peak fertility. 2 months ago we didn't get a peak, just several high fertility days. Last month we got a peak. We've been testing 2 times a day to catch the peak this month but it should have come today and so far the OPK still only reads high fertility. 
What's the deal? Is it common to only ovulate every other month? 
Any info/advice would be greatly appreciated!