I think I know what you mean, I get it sometimes in brief moments when I think, 'Am I dead really? Is this world real or am I imagining it all?' etc. I think of it as being 'crazy-making', as in it destabilises sense of self and leads to doubting your own sanity.

You say you've been having weird dreams at night but you haven't detailed them, what happens in them?

Has anything changed in your life recently? This can produce weird dreams. Are you sleeping properly?