Implantation bleeding?

Tara • New Zealand 🇳🇿
 I'm curious to know if anyone else has had implantation bleeding around 5-6 days after conception?  I use OPKs every day and journal all my info so I have a fair idea of a conception date ( IF it's conception, which I highly doubt)
I've never experienced spotting days after sex and ovulation before. 
Thanks