I think that whatever was in the trigger that caused you to surge is still in your system and therefore registering a "false" positive on the OPK. A few cycles back I did a trigger shot and I was concerned about whether I did it correctly or not so I took an HPT to be sure. It registered positive immediately so I knew the HCG was in my system. From what I understand OPKs can read HCG like it reads LH so it can show positive if you have enough HCG in your system. Good luck!