Read through briefly, and I'll read through again, bit by bit!
The first stanza sets the tone of the poem, right from the off: "Anxiety hangs over me like an impenetrable cloud...." and the fact you write "bringing a sudden sense of fear" makes me wonder if this anxiety itself is new.
I think the second stanza confirms the above suspicion - you have only just come to this anxiety because you have only just accepted or been awoken to reality: ....."reality has become my enemy."
The third stanza, for me, is heart breaking. An admittance of lost sanity because of the acceptance of reality. I guess it's often the horrors of reality that bring the affects of insanity for so many people. "......and the last remains of sanity escaped without a trace." - a thoroughly moving line.
And then the final acknowledgement - reality and the resultant anxiety has become too much for you to bear and insanity has taken over and you have become "lost".
This is another truly moving and emotional piece, Saffie - well written.
All the best,
Ben