Strange symptoms?

I've been having certain symptoms for a while, but many doctors can't find anything. Does anyone have any ideas? These symptoms are bothering me, and I need some advice on how to resolve them. I have constant mild headaches, I can't lose weight no matter what I do (and I've tried a lot) and just…

Is there a natural limit to the frequency with which humans/animals can voluntarily move their limbs due to nerve impulse transmission?

What I mean is that male hares, for example, drum their hind legs on the ground quickly one after the other to warn rivals. Muscle tremors also always seem to have a similar frequency. Or is that just an illusion?