Your body can try to ovulate more than once in a cycle. If your body fails, then It will try again a few days or a week after. Your results might not be accurate if you're still using the coil too.
You may be one of those unlucky women where OPKs don't work for you or.....you may be use AF or already pregnant like the PPs have said. So many rthings to consider on the TTC journey!
A BBT might be a better way to go if you're looking to get a better understanding of your cycle. Good luck? Xx