Empty
You know that feeling that you're drifting through life - a ghost - moving on autopilot down the corridors in school? It's so cold inside of you, like there's a literal void inside that is slowly growing and growing like a tree. Like a tree, you hope it will die, but it will probably live for way longer than you will because you don't know how to cut it down.
All you can focus on is the inside. The inside of your head. The inside of your heart. The inside of your soul. Hoping that they won't be engulfed by the void just like how a phagocyte engulfs a pathogen.
The sounds - laughter, talking, walking - they all amplify in your head as if there's nothing in your head and it bounces off the narrow walls freely.
But there's still nothing. Everything is still empty.