Scared of New Worsening Depression?

As I'm writing this, I'm calm and have had time to cool down and really think about what happened today. For a bit of background, my "normal" depression is usually heavy and gloomy, usually tired and really hard on myself. Well today, around 11am in the middle of class, that shifted unexpectedly.

When I sat down it math I felt different. Depressed but different. It felt cold, distant, and quiet. Even though the sun was hitting me in my hoodie, the class was being loud, and I wasn't sitting too far from everyone in the class (even though I sit in the far back), it felt odd. The cold didn't make me shiver, or need more layers of clothing. It was just a feeling. And it felt quiet, like my mind's senses were being clouded (which is true, because the whole day after that felt so foggy that it felt like a dream). I felt like I was the only person of earth. Instead of feeling heavy everywhere, it was just my shoulders and chest, but my head felt light and the rest of me felt like I was floating, and the atmosphere around me was so dark, almost as if the lights weren't even on. I felt like I could close my eyes and imagine everything in a dark blue, saturated tint.

I remember being scared and anxious, because all I could think was "I hope this isn't what people think before they end their lives," and so for the first time I tried to draw blood through self harm. I only ever used ice and rubber bands, but I clawed and scratched at my arm, even though I didn't do it out of hating myself in anyway. Just out of this new feeling. Out of fear, not anger.

So has anyone else ever felt depression like this before? Is it a bad sign? Should I call someone? I don't want my life to end yet, I'm too young, but I'm scared.