AF due the Oct 21st

Erin • IVF warrior. 🌈👶🏼 born 6/24/21 after 5 years.
When is the earliest I can even consider testing? I never caught my 100% positive on opk so no idea truly what day I am post ovulation, or if I ovulated. 🤔 Having tiny twinge cramps today wonder if I have yet to even ovulate. So confused!