Starting opks *advice please*

Soooo, I had my coil out (Mirena) & LLETZ done 10 days ago and I want to start tracking my cycles so I can get my head around them before starting to TTC in December. When do people start taking opks to look for their peak? I’ve been doing one daily just to keep an eye on what it’s doing since I haven’t had a period since 28th august. I’ve had bleeding since the LLETZ procedure which I had no cramping with & it’s nothing like my usual period so I’m assuming it’s just bleeding from the cervical wound. I’ve never had anything more than a VFL on the opks. What cycle day would people usually start testing?

Any help welcome! (I always had a period every single month until September when they just randomly stopped)