Male canary is not right

by Lucille
(Hillsdale, NJ , USA)

I have a male canary ducky who use to sing beautifully, it eats an awful lot and can't seem to fly, he tries and sometimes he makes it to the perch and sometimes he drops to the bottom of the cage. His buffed often and stays in his eating dish or the bottom of the cage. Not sure what to do for the poor bird. I've had him for about 4 yrs! His been like this for over a month and a half. Please help if you can. Thanks