Haha! I went and filled my pee cup again and used two OPK's, a home health one and a wilkos one, both 20 miu/ml- much darker lines than the HPT's. My theory is that the HPT stays lighter longer until a certan lvl of HCG, whereas the OPK's need to be very precise in the darkness of the line what with it having to detect fluctuating LH. The lines on these OPK's are a similar shade to the opk at the beginning of my last surge- slap bang in between the lightness of a - and the darkness of a +.