TMI PICTURE my underwear keep getting stained?

30 weeks pregnant

This is not active discharge, it's a dry stain from a type of discharge or something but idk from what. When I wipe everything is clear, never thick or discolored and I swear to god it's not poop. I'm a very clean person so wtf is going on with me the last week or so?

These undies were white when I put them on this morning!