Shaking is often a response to pain so I think that there is more going on here than your original vet realized. I suggest that you return to the vet and get some help.
I do think that you need to see the vet this weekend and find an after hours vet to help you. The neurological symtpoms worry me, as does the lethargy and lack of appetite.
The most common cause of lethargy and loss of appetite is a parasite problem.
Since you are seeing shaking and and a lack of motion, you should be concerned that there is a back or spinal injury.
Let me know if you have more questions about this.