Has anyone ever had this?

2 days ago, I had this stringy mucous/blood thing. That was all it was. No blood or anything since.

I thought for sure AF was starting, but no.

So I thought it was a good sign, and took a test this morning @ 13dpo. But it was negative.

The only symptom I’m having is sore nipples. My usual AF symptoms are dormant.

P.S. 95% sure anything you see is an indent.

Edit: Using OPKs & bbt to track. Please note that I stop tracking bbt after it confirms O, so I am not 3dpo.