It is recommended that you do not test with FMU
as this has a larger quanity of the naturel amount of LH.
Our bodies always have a certain amount of LH hence the lighter line
that is always present.
You can test anytime of the day other than then.
I read somewhere that no matter how long your cycle is that most women O
around cd12-14 so id keep testing.
But... and this is just my opinion... I have used OPKS quite often and we have been ttc
for almost 20 cycles now and they seem to do nothing.
They are not fully reliable as they 'predict' O. They cant say for sure you have O,d
as there sometimes is something that prevents O. Be it stress etc.
But the prob with the OPK is that it would still show up the surge...
I leave things to nature nowadays but hey thats just me
Good luck
Sarah