The astral plane is pretty much another plane of exsitance. So your not dreaming, your projection your astral body..pretty much your etheral energy into this astral plane. Everybody goes here when we sleep, we just dont remember it. You can astral project from a lucid dream, i have done that a few times by accident. I dont exactly remember how because i havnt practiced this stuff in a long time, my interest has started to return now.

The reason stuff in your room has changed is simply because the energy of other physical objects that used to be there still remains. After awhile those objects will dissapear and your room will start to look more like your room. But it takes a LONG TIME.

This is what i have learned in my studies of all of this. But everything is subjective so my explanations may be completely different from others so dont take my word for this lol.