Today is cycle 5, CD11. In previous months I've used OPKs they've turned positive on CD15, then CD16, then CD21 last month (grumble). My acupuncturist is convinced I'm going to 'regulate' and fall back closer to CD14. What day do you think I should start using OPKs?

I only wonder because I'm using digitals so would hate to start today and go through half a box or more and waste them. I would also hate to miss O. I suppose I could use the internet cheapies and when they start fading in, switch to digitals, but I don't have any on-hand yet. What do you all think?

(ETA: i know to BD this whole time regardless, but I'm getting tired wasting my money on these expensive OPKs so want to maximize them! )