My cat is having full-body spasms and no one knows why!

He has been having full body spams for a month now. He's had x-rays, bloodwork, and epilepsy medication. Nothing has shown up, and nothing has helped. He is still eating, drinking, using the washroom, and playing, but whenever he lies down, he is bothered by spasms, including while he's sleeping. They do not stop! He's only 1. Very young. He may also be vomiting semi frequently, but I'm not sure because I have two others cats and perhaps it is one of them. He seems frustrated - he runs around and meows with frustrated anxiety, and he purrs too much - I know that can be a bad sign. I'm terrified that he is in terrible pain, or that he is slowly dying, and I have to watch him, because no one has been able to help me! He must look at me and wonder why I'm letting him hurt I'm horrified. Here is a link to a video I posted, showing what is going on: