Writer's Block

What I don't understand is why I can't write on command anymore. I used to be able to rock out five page papers in an hour, but now I'm stuck in this rut that clogs up my creative flow. When I write, I want to put at least a little bit of meaning or flair into each piece, but lately I feel like I'm writing papers that are unoriginal and boring to read. What's wrong with me? This feeling has been going on for a while now; even when I do feel like I'm going somewhere with a paper, it'll stop a few minutes later, and I'm stuck in that same rut. I was so excited to write my profile paper on an upcoming writer/director/editor/actor, and I was off to a good start, but every time I sit down to write more, I instantly hate it. I've tried just writing and allowing my words to flow out, but even then I get stuck and have a hard time finding the right words. All of my writings have been crap lately and I have no idea of how to fix this. I used to love writing and couldn't go a day without it, but now I'm finding myself going months without ever being truly happy with my work. Being too critical of my work has caused my grades to lower considerably, but I just can't bring myself to turn in such trash and having other people read it and think I'm an idiot and talentless writer. 

What happened to me?