First time using opks... advice please

[lillichloe]

I came off of the implanon bc implant about 5 months ago was on bc pills for a month and a half after that. I am on my 4th cycle after not having any for 3 years while on the implanon. This will be our 3rd month actively TTC. 3 of my cycles have been spot on 28 days. This last cycle was 27. what day CD should I start using opks? I am on CD4 and think I am on my last day of AF which is normally 5days. Any help is appreciated.

 

[mommyof5]

Heres a chart https://www.fertilityplus.org/faq/opk.html