Writer's block

Somebody help me! I am suffering from a writer's block and please don't tell just start writing or brainstorming. It has all proved futile.
For some reason I have become prone to writer's block more often than before. I could spend hours on end evaluating different views, critically analyzing them, and formulating my own arguments just to find out that someone has already thought similarly.
It is frustrating because I am lagging behind in all my projects and many of them are past due. It's affecting my morale and I feel further sluggish and disheartened.
Why is it happening?
Ohh goodness this is so galling!!!!