What mucus is this????

First of all, I'm 1 year pp and I've only had 1 very light period. I'm using the copper IUD as BC. I am weaning off of breastfeeding.

During random days of the month what I can only assume is mucus starts hanging from me. I use the toilet and this mucus is hanging like snot from my vagina all the way to the toilet water. What and why????