That sinking feeling

There's that slightly nauseous feeling you get when you're nervous. Your fight or flight mechanism kicking in, as if puking your guts out in front of whatever potential threat there is will help you do either, unless projecting stomach acid at your enemies is a useful weapon.

I have that feeling now, and I'm sitting calmly in a library, tapping away on my iPad. There is no threat present, I am not stressed and there is no possible reason for my anxiety. And yet I still feel like my stomach is being sucked out of my body by an ethereal vacuum cleaner. 

I reflect on the past few days. Nothing much has occurred. 

The boy I like said hi and I tripped over a chair at him. I'm teaching my pet American to speak English. I suspended my brother by his ankles and shook him only to find a teacher watching in horrified fascination.

So why do I have this feeling of dread? As if there is something around the corner that I detest, but I can't quite put my finger on it. A curious nagging sensation which I allow to fill me in the presence of all other emotions being impartial. 

Then I realise, that once again I have not done my maths prep. Oops.