Hi April, I used OPK too and when I went for my first ultrasound (vaginal also), the doctor said the dates matched exactly with what I had told him. Maybe you got pregnant before using the OPK, I mean maybe you conceived a week before and tought the OPK was what did it? I know many people get positives with OPK when they are actually not ovulating. This is all I can think of, sorry. Sally 2