My chick can't stand and keeps moving his head like crazy

[Sara 212]

Hello everyone, I'm Sara i'm new here..Umm i have a 5 weeks chick it's been very healthy till today when he started to move his head real fast ..and he just cant walk ..his feet cant hold the weight .. he used to run really fast now he's all messed up, but he's still eating alright though..his eyes keep closing also, PLEASE help me !!