I was in the shower and I sneezed into my hand. No biggie, I'm in the shower, it'll wash off. But right before I washed it off, I noticed there was some black stuff in it. And I just sneezed again, and there was small bits of black stuff in the tissue. I've had small amounts of blood like this before, but this isn't blood. I have no clue. It looks sort of like.. mold? I've had bad sinus headaches for the last week or so, too. What is this?!