you've been hard at work at it, so go ahead and post it! it's no use letting something develop dust once you're finished if you don't want it to
even if the setting or situation happens to be the same, it's still not the same story. it might even be better if you posted it sooner if you're worried about people comparing (esp if it's a longer fic then it obviously shows you haven't copied the other writers idea on a whim)
it might also help to read the other authors fic if you haven't yet. stand tall anon