Your not supposed to keep testing after you get a positive. Almost all of the boxes for those test tell you that.
The reason is because the LH can remain in your system even after you ovulate. Once you get a positive it means that you MAY ovulate in the next 12-48 hours. The OPKs aren't very accurate because women can have LH surges that do not preceed ovulation and then could end up missing their ovulation because they think they've already ovulated.
It may have been darker because there was more LH or it could have just been a more sensitive test. Test sensitivity can vary between boxes and even between test in the same box!
Get the book Taking Charge Of Your Fertility and learn to chart. Charting is much more accurate, less expensive and there is no guessing unlike the OPKs.
GOOD LUCK!! BABY DUST!!
at 2:16 PM on Nov. 8, 2010