Heva, it is possible that you will ovulate in the next 12-36 hours. However, it could also be that your body is gearing up to ovulate and doesn't. I got 2 positive CB digis this month on CD15 and CD18. Then I got another one on CD25. I ovulated on CD26. The OPK detects the LH surge before ovulation. You can have a surge and then not ovulate. You should keep testing with OPK's if you usually don't Ov this early.