For the past few days now, my back has been feeling really strange. It has felt really weak, like it doesn't want to support me. It's all I can do to sit or stand for long periods of time. I have never had back trouble before, and while I'm not in shape, my muscles haven't been horrible. I don't seem to have any other symptoms of anything so I don't think I'm sick. What else could be causing this? It doesn't hurt but it's really frustrating/annoying!