I am sorry to hear of the problems you are having with your cat. It sounds very familiar to the problem I've had with one of my cats for several years, and I think I'm getting a handle on it now. It sounds like it might be Feline Hyperesthesia Syndrome (FHS) better known as Rippling Skin Disease or Rolling Skin Syndrome.
I am enclosing a couple websites for you to have a look at. One has several videos that could be of interest, and the other is how to identify the Rippling Skin Disease.
When Yogi had the problem I found that a good diet helped, and playing with him helps to take his mind from the problem when it happens. I also put Rescue Remedy in the drinking water every day, and when he was having a spasm I would put a couple drops in between his toes on his front feet or behind his ears whichever was easiest.
Check the websites and see if this is the problem you are having. If it is you won't need Prozac. If this looks like what is happening, let us know and I will go over what I have done in order to bring it under control for us. You can see if it would be of any value to you.