I had a look online it says for 35day cycle to start testing around cd18 but me personally I would prob test few days earlier if using cheap opks... Once start to see it darkening try a few times a day hopefully to try and catch the surge as the test line will go darker than control line or as dark...
Hopefully though this is your month but if not and test next month all the ladies on here including myself will help you with the surge when you see it getting darker but I hope more this is still your month xxx
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