The Stormy Search for the Self by Christina Grof & Stanley Grof is a must read for anyone going through utter darkness. The feelings of lonliness section greatly described my experience:
"The Great Separation was here... a peculiar, special feeling of utter loneliness... It cannot be compared to any feeling of loneliness we all experience sometimes in our lives. All seems dark and lifeless. There is no purpose anywhere or in anything. No God to pray to. No hope. Nothing at all."
The Chasm of Fire, by Irina Tweedy
And the complete alienation was upheld with the belief that even death wouldn't bring solice:
"...they have the insight that even suicide is no solution; it seems that there is no way out of their misery..."
~ The Stormy Search for the Self by Christina Grof & Stanley Grof pg. 52-54.