Help! How to help save my fancy goldfish! :(?

This sounds like it is most likely gas bubble disease. Symptoms include bubbles in the fins and beneath the skin and tiny bubbles on the sides and ornaments in the aquarium. You can see if your water is over oxygenated by placing an empty pop/water bottle in the tank and filling it and sealing it under the water. Set the bottle on the counter and wait 5 min. If you see tiny bubbles forming on the walls of the bottle your water is over oxygenated. I would turn the air pump off but leave your filter running to prevent ammonia buildup. If gas bubble disease is caught early they can recover but if it has gone too far already they may not make it. Hyper oxygenated water can be the result of either too much turbidity in your tank or it can come from your water source in your house..