Downside Up

I know something is bothering me somewhere deep in my subconscious because I feel very conscious of the world being a globe floating, rotating in space.  I feel very aware of being in my bed with continents and magma beneath me.  I feel precarious. And I feel like the world could just fall, like it could stop orbiting and start plummeting into the universe.  I feel like gravity could give way and the world could fall down and I would fall up, up into the atmosphere until I exploded.  I think about how horrible it would be to fall up.