It is not a happy experience but I have felt this a lot. The sense that, whatever you do or say counts for little or nothing. Still, I am in good company. Although this was not intended as a religious treatise, read the melancholy words of Mother Theresa, for instance:-
“Lord, my God, who am I that You should forsake me? The child of your love - and now become as the most hated one - the one You have thrown away as unwanted - unloved. I call, I cling, I want - and there is no One to answer, no One on Whom I can cling. The darkness is so dark, and I am alone. Unwanted, forsaken. The loneliness of the heart that wants love is unbearable. Where is my faith? Even deep down, there is nothing but emptiness and darkness. ...If there be God, please forgive me. Trust that all will end in Heaven with Jesus. When I try to raise my thoughts to Heaven there is such convicting emptiness that those very thoughts return like sharp knives and hurt my very soul. Love, the word, it brings nothing. I am told God loves me, yet the reality of darkness and coldness and emptiness is so great that nothing touches my soul."
There can have been few saints subject to such doubts about the very existence of God as this.