I have a whirlpool washer. All of a sudden a light load would go unbalanced and even an empty load wouldn't be balanced. It's much more sensitive with loads even light 2 or 3 items loads.

You have a broken spring or spring support. You will have to look at it to see why it is doing this. Frequently, this will happen when the spring hole rusts out. Drill another hole and put the spring back on or attach a piece of metal for another support.
Here is a manual: https://dl.dropbox.com/u/8010163/Understanding%20automatic%20washer.pdf