Question for the chart experts - two possible O dates

[marmoset]

OK, here's the situation:

FF first gave me dotted crosshairs at cd12 based on temps alone. Then when I had EWCM on cd14 it moved to solid crosshairs on cd15.

HOWEVER I had a huge dip below coverline on cd20 (no change whatsoever in temping circumstances).

So if that was an implantation dip (I know that's not certain by any means) it seems to me that I have two possible scenarios each with an unlikely aspect:

Either I o'd on cd12 and had EWCM after O (odd) but an implantation dip at 8dpo (normal).

Or I o'd on cd15 and had EWCM before O (normal) but an implantation dip at 5dpo (odd, that's really early).

Any thoughts on which is more likely? Or put another way, which is more UNlikely, EWCM after O or very early implantation?

Here's my chart! Opinions welcome.

https://www.fertilityfriend.com/home/5d169f/thumb.png
My Ovulation Chart

 

[AngelOb]

I would agree with your.cross hairs and put O on the cd15. Mainly because of ur cm tipping you off to it.