Im new and have a question about my shih-tzu

Hey my name is Mark. I have a 2.5 year old Shih_tzu named biscuit. i recently took him to the vet for an update on his shots and the tried a fegal exam on him for worms which was negative. his tail had gotten matted up so they also shaved his tail. ever since we left the vet (which was a week ago) he has been walking with his rear end shifted up towards his head. we took him back and they have done multiple test on him from neurological to checking his liver to xrays etc etc. this had been over a week now and still no progression. if you throw his ball he will run straight and fetch it but when he walks back he walks sideways. they have no answers for me and this never happened before he went to the vet a week ago. any suggestions as to what could be wrong? could it simply just be that he was traumatized from them shaving his tail? i am at a lost and he doesnt show that he is in any pain but just has the issue walking. thanks in advance and thanks for having a site like this.

Have answered you in the other post.