Why doesn't my budgie talk anymore?

Hey Guys,

It’s been more or less a week since I realised my budgie has stopped talking and behaving like he used to. He has always been very playful and makes a lot of noise, but now he sleeps alot, eats at odd times and overall doesn’t look so good. My mum says he’s just old because we’ve had him for two years. It’s strange though it’s like he’s turned old in just one week. Please tell me what to do.