Opk questions, newbie here!

Hey ladies,

I had a chemical in August (started bleeding the 11th through till 17th) anyways this is my first time using opks (I didn’t have any at the beginning of my cycle) and I’m a poas addict 🤭 so when I got my hands I decided to take some, anyways cd 26/27 and now 28 I’ve had blazing positive opks - the lines were there and getting dark before the control line had even started to work (how I wish they were hcg tests haha!) Wondering if I’m ovulating late because of the chemical but how long do yours usually stay positive for? Is this normal? Never used them before so unsure, any advice/input welcomed ☺️

Top test is saturdays, middle yesterday and bottom today