Questions about ovulations and OPK.

Hey! So i got my first positive ovulation test 2 days ago. This is my first time trying them so i kept testing. Yesterday it was positive and today was negative. How long are you considered fertile after that first positive opk? Am i still considered fertile today after a negative opk? I tried googling but didnt find exactly what i was looking for. I havent had any ovulation pains or anything like that so i dont know exactly if or when i ovulated. I started doing my bbt this month too but quit because i was failing at that.