Your kitty needs to see the vet immediately. This is indicative of a neurological issue.
I know I'm going to start sounding like a broken record but: our kitties are being broken by the food we trust to nourish them. I'm SURE you have taken her/him to the vet already, what did they say. If your feeding Wellness AT ALL he needs a B-1 shot, don't wait for more tests. It won't hurt him and might even be too late but try it. Looking back through pet food recalls over the years, as I was new to caring for a cat, The main pattern seems to be- if it happens to one or two brands/flavors, that's just the beginning. There are only so many distributors for "raw" materials in pet foods. If one brand is tainted more will follow. The recalls are too little too late. I fed my boy Wellness for years, with good results, April 2010 he started having GI issues- never occurred to me that the food that had once healed him could be now be making him sick. The long story, I posted on city- data.com/forum/cats/1278743-elderly-cat-cant-stop-eating-3.html (Not my title) The short story is, even if the blood work comes back "fine" make sure you test liver function, electrolytes, vitamins and minerals . Also check for heavy metals especially zinc and lead. Owners are having Wellness cans tested and finding high levels of zinc that are then confirmed in their cats' blood work. Anemia, it's there, find it somehow, look for Heinz-Body anemia, May be an increase in numbers of eosinophils in the blood. That a clue. I learned this and so much more too late and the hard way. I pray your kitty is o.k. He's lucky to have you.
I may be over simplifying things but could your kitty have blocked anal glands. Thats what happened to one of my cats one time and she wasnt walking straight. After the vet expressed them she was fine. The vet told me that he would show me how to do it myself but I told him that that was not necessary because I would never do it myself. Also you didnt mention the age of your cat. My 13 year old cat cant walk straight because she has arthritis in her back. I hope you find answers soon. But you probably should have a vet look at your kitty.