I wonder then whether it's my monitor. Towards the top of the photo, the sky shows up as distinct patchy bands of darkness rather than a smooth gradation.
I have 22 inch monitor and what I see is banding or clustering, barely perceptible, where the sky turns from dark to light rapidly at the top left just to the right of the most left tree. IMO this comes from altering the contrast-brightness controls too much. I have done this myself and your image has an infrared look which often produces this kind of banding or clustering and makes part of the image unrealistic looking. Try a one time BW conversion paying close attention to the contrast alterations. The more you alter your image at the extreme ends of the contrast-brightness controls, the more this kind of look will appear.
As much as I like the composition, the lighting looks unrealistic. But perhaps that is the look you are going for.