Hi!
OPK test line has to be equally or darker than the control line. IF you go to my journal (link below) you'll see a pic of all my OPKs. I kept getting them with a really faint line hoping that's IT, but HPT are the only ones that are read positive with a faint line. OPKs with a faint line are negative. Anyway, if you see my picture, you'll see how I used to get faint lines and then a day or 2 before I OVed I started getting them darker and darker (I would recommend to do 2 per day, morning and afternoon because sometimes the LH surge will happen for 15 hours and then you'll miss it if you OPK once a day) Once you start noticing them getting darker do 2 per day and then you'll get a +OPK a couple of days later.
A +OPK doesn't necessarily mean that you will OV though, it just means that your body is getting ready for the release of the egg (we don't all ov every month, it varies) If your BBTing and you get a +OPK and then the next day you see a drop in temp in your BBT chart, then that means for sure that you OVed.
Hope this helps and good luck!
