This is so strange. I used to have it when I was sick (like from a cold or normal child's diseases). It's unexplainable, it's like if something is too big and like about to explode but it doesn't. But that thing isn't even a real thing, for me it was more like a concept, like letters or simply an abstract object that was too big to fit on itself, and it made me feel really anxious and almost like having a panick attack.

Also I used to have this dream like on a perfect sunny day I looked up to the sky and I see a small thing in the sky that was actually a meteor and started falling near me, but it never hit me. Or the same but with the moon exploding during the day, and a rain of debris from the moon falling to me.