My cat can't move!?!?!?!?

Thank you for taking the time to read this. Just looking for advice or possible answers. Here is the story. I woke up this morning and my cat was walking like his foot was asleep. (Right front) At first I brushed it off, he just woke up too so maybe it was asleep. But then he jumped up on the bathtub ledge like he always does and fell face first into the tub. His foot still wasn't working. I called the animal hospital and they told me to bring him in. So I took the morning off work and took my cat in for an examination. This Dr. was lousy. he felt her leg just like I did, told me it wasn't broken, which I already knew, and then said I needed an MRI. He said to crate her for a week and then call him. So I took him home and went to work for 4 hours. When I got home, he was worse! His back leg had now quit working. They are both stuck at the elbow straight out. So I called the emergency vet since it was now after hours. They told me to bring him in and were so much better. They weighed him and took his vitals. They then told me they have no idea what is wrong. There are a series of tests they could run but its all chance and very expensive. They said it is most likely neurological since it is all on the right side of his body and he isn't feeling pain. so they put him on steroids and antibiotics. They also told me the other side of his body is weak. It's strange because he doesn't seem to understand his body inst working. Now, he cant flip up his paws, and cant even sit or stand. He just lays there. Does anyone have any idea what is wrong with him? He is about 5 or 6. Indoor cat. NEVER been outdoors in over 3 years. Male, Neutered. 7lbs. All this started this morning, at 730 am. so within 14 hours he went from not being able to use one leg to almost his entire body.