You're going to either have one more cue peak by CD18, or you're going to not have one at all. At this point, you're going to have to go by vaginal readings. Unfortunately with us long cycled women, we do get various times throughout our cycle that we will get a peak. So you're fine, I had the same thing. Wait til CB changes from low, then start looking for a vaginal low.
I have the classic, but from what I understand there's a slightly different color that shows when the ovacue picks up on secondary fertility, and you MIGHT get that to happen.