Hi,Customer and thanks for your question.
From your description, it sounds like your dog may have a neurological condition called Vestibular Disease; this causes a dog to walk or stumble like he's drunk, act dizzy, and sometimes nausea or decreased appetite is also apparent, as a result of the dizziness.
If your dog had any opportunity to lick or ingest antifreeze, it can have similar 'drunk' type symptoms as Vestibular Disease. In addition, an inner ear infection will cause equilibrium problems and dizziness.
Weakness in the hind legs may also be associated with diabetes (diabetic neuropathy), a heart condition called cardiomyopathy, and other underlying medical conditions.
Try to have your dog seen ASAP, by an ER vet center, if your vet is closed at this time, so he can be definitely diagnosed and then, treated.
I hope he's feeling much more comfortable, very soon, and all will be well!