I have SO been where you are. It's a terrible feeling! I get amost panicky. Then when I sit down to write I cannot even force myself to think about it. But, I have found something that helps me (usually). I go somewhere, most often to a park or maybe a quiet drive in the car, and daydream about my work. I don't plan anything, I don't plot anything, I just think about the story I have so far, what it would be like to be one of the characters perhaps, or perhaps I'll just go over a favorite scene in my mind. Before long, I find myself beginning to plan and plot naturally. Things start coming to me on their own, and soon I can't wait to get home and write. This usually works. But sometimes I've had to do it a few times before my mind frees up enough to where my creative juices are flowing.
Hope that helps. Best of luck, and let us know how things turn out. :)
"Don't only practice your art, but force your way into its secrets, for it and knowledge can raise men to the divine."
~ Ludwig van Beethoven