My 9 week old won't drink his milk and is cold and clammy..whats wrong ?

If he is still cold after putting another layer on and he has not been interested in his milk for a couple of feeds then I would go and get him checked out straight away - when it comes to kids especially babies - trust your instincts - even if it seems silly take him to the doctor, if it turns out that he's fine at least it will reure you.