I wish I had known that positive OPKs can be false. Well, maybe not false, but premature. This month I had a positive OPK on cd16, but didn't O (according to temps) until cd19. If I hadn't been temping, I might have quit BMS too early. In looking over my previous charts, I can see that this is the third month out of eleven in which this has happened. One of those months, I was 7 days late for AF (or so I thought) and when AF showed up I was convinced I had a chemical pg. In reviewing my temps, though, I can now see that my OPK+ was premature. According to my temps that month, I started AF right on time. This would have been helpful to know before!