Have you seen a physician about this?
If it is psychological, it may be because you are dissociating from a trauma of some sort.
I remember when my brother got hit by a car and was put into a coma, nothing around me seemed real. I slipped into solipsism. That is, I felt like the world around me and everyone in it were figments of my imagination, products of my mind. Because reality was painful for me, I think I was trying to protect myself from it by removing myself from it.
In any case, you shouldn't go through this alone. Go see a doctor.
