How was the writer sure that he was not asleep?

Answer:

He had a welt next day
Discussion:
It was a summer night. I was not asleep yet, not even tired. I was just staring up at my ceiling when I heard what I thought was something at my window. I was always scared of nonsense things from watching 
to many horror movies, so I was reluctant to look through my window shades into the night.
The noise continued as I just stared at the closed window shades. It sounded like scratching or dull scraping. I tried to ignore it and lay down, but it continued, getting louder and louder. I know that it was not a dream because I was fully conscious and 
even pinched myself so hard I had a welt the next day.
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