Yes, I would get a cat scan for the next step! If it's causing you a lot of problems, you'll definitely want to try to figure out what is causing it. Do you get any other symptoms of anxiety? I wouldn't think it would be anxiety if dizziness is the only thing you feeling. It's common to feel it as an additional side effect if you have other symptoms of anxiety though, and expecting the feeling of dizziness can actually keep you dizzier for longer! But yes, if I were you I'd go ahead and get the scan to see if that can determine anything else.
I hope that when they took blood tests for your heart, liver, and kidney, they checked for other basic items, like your blood sugar, thyroid, anemia, etc. Do you know if they did this? They should have if they checked for everything else, but all of those items can cause dizziness as well. Those would be the easiest to identify though!
A few other things - a stressful lifestyle, being slightly dehydrated, eating habits, under- or over-sleeping can also be things that can cause dizziness. I also know a person who had a food allergy causing dizziness. It got to the point where they would pass out. Turns out they can not eat any gluten or artificial coloring. So, that pretty much had to completely change the way they ate! There can be so many different things that cause dizziness and I hope you are able to find what's going on!