Early OPK

Cycle length: 34/36 days
Duration of AF: 5
Normal ovulation day: CD21
Hi all, I'm so confused. Please don't read and run.
I'm currently on cd9
My af this cycle only lasted 3 days then on the 5day I had spotting.
I got a positive opk last night at 10pm cd8.
Surely it's too early to ovulate?
Please, any help would be appreciated! Thank you!