I took an OPK last night, and got a negative. I checked after 5 minutes, after 10 minutes, and after an hour, and the results were much the same: a slight negative.
This morning, when I retrieved the test, it had suddenly turned into a blazing positive. I am used to OPK strips staying generally in the same vein. If lines get darker, they should both get darker at the same ratio right?
Any possible explanation?