On the 7th or 8th night after Madeline's death, why couldnt the narrator sleep?

The narrator couldn't sleep because due to an inexplicable nervousness and raging storm.

It was, most especially, upon retiring to bed late in the night of the seventh or eighth day after the placing of the lady Madeline within the donjon, that I experienced the full power of such feelings. Sleep came not near my couch — while the hours waned and waned away. I struggled to reason off the nervousness which had dominion over me. I endeavoured to believe that much, if not all of what I felt, was due to the phantasmagoric influence of the gloomy furniture of the room — of the dark and tattered draperies, which, tortured into motion by the breath of a rising tempest, swayed fitfully to and fro upon the walls, and rustled uneasily about the decorations of the bed. But my efforts were fruitless. An irrepressible tremor gradually pervaded my frame; and, at length, there sat upon my very heart an incubus of utterly causeless alarm. Shaking this off with a gasp and a struggle, I uplifted myself upon the pillows, and, peering earnestly within the intense darkness of the chamber, harkened — I know not why, except that an instinctive spirit prompted me — to certain low and indefinite sounds which came, through the pauses of the storm, at long intervals, I knew not whence. Overpowered by an intense sentiment of horror, unaccountable yet unendurable, I threw on my clothes with haste, for I felt that I should sleep no more during the night, and endeavored to arouse myself from the pitiable condition into which I had fallen, by pacing rapidly to and fro through the apartment.