Implantation dip?

Melissa
Is there such a thing as the "implantation dip?" Or is it myth??
I have been since 28th (1dpo) 36.3 and today bbt was 36.1. Now this is my first month temping and I'm not sure if the implantation dip exists? And if so is it a huge dip or a little one? Any advice definitely welcome x