Hiya, it's my first cycle of using OPK's and I'm getting confused by the results. Yesterday morning around 11am I tested and had a positive, then tested again at 5pm and it was negative. I thought excellent I have seen the LH surge. Then today, out of curiosity I tested again, it looks positive to me. Do you think yesterdays was just a faulty test? Can your surge last over 24 hours. I'm confused!