Fish tank smells like death...?

My fish jumped out of the tank about four days ago, not sure how long it was out, it was still alive when I found it so I put it back in the tank. Since then he's turned a whitish color and produced more slime than normal, plus his scales seem to be falling out-I understand that he's on the brink of death, but he's not dead just yet....the tank, no matter how much I seem to treat the water always has a high alkaline reading, and I changed the water last friday night becuase the tank smells like death, but then again this morning it smells like death....Any suggestions?