OPK's work as preggy tests as the hormone is almost the same. The preggy hormone has a little more to it, so opks will work as preggy tests but preggy tests don't work as opks because they are lookinh for a slightly more complex hormone. I would guess you may have just got your bfp. Anychance you can get your hands on a preggy test today? The otehr thing to bear in mind is that you can get a slight reading of luthenising hormone at most times of the month as the hormone is always there. Was the line dark and definetly positive or just faint? If dark then jump on a preggy test.
P.S - sorry for the overuse of the rather annoying term 'preggy test'
Good luck,
B
Good luck.