Ovulated on the 15th or 16th

Ashley • TTC baby #3.... Hubby had vascetomy reversal done in August 2014. We have two boys (8&9). Hoping for our baby girl!
If I ovulated on the 15th or 16th according to my OPK. When should I be able to test??? I tested the 23, and today(25th) with BFN