ok here's my question. Do I have to redwraw every frame that I do in my animation or is there some other way. Because if you redraw every frame then the figure has different proportions every frame.

Onion skin. Use it. Live it. Love it.

Just work on every frame a lot.

And zoom in to around 400% + use the grid lines. You can acess the grid lines from the "View" rollout. Aswell as them, trail your movements and use more frames. Dont tween whatever you do, and try stay away from the free transform tool, unless you are resizing, or easing into a walk/run.

but I have seen flash animations where the stick is always exactly the same size

thats because they are extremly good at drawing it again, onion skin helps but its just down to sheer practise that lets them do that