Help with my goldfish!?

The white stuff on your fish could possibly be a common fish disease called Ick. It's white and usually the fish starts to look 'dry' which since they're in water it doesn't make sense, but it's true. They become slow and barely move and look quite weak. I suggest removing your fish from the tank into a separate bowl or something to see if it gets better, if not it most likely will just die and or spread the disease to your own fish. You can also buy tablets at a pet store to treat Ick.