Just take a break from it. Listen to all kinds of music you wouldn't normally listen to. Read up on your equipment, anything that will progress you through your slump. I usually just stay away from it (making music in a slump), don't force creativity. It should just come to you, you force it, it will come out shitty. I have been going through the same thing lately. It's all natural, everyone gets it. It means you got too much on your mind. Just relax, smoke a fatty or something, watch a movie....