What Causes Persistent Dizzy Spells?

For about 2 months I've been feeling dizzy. I don't feel light headed but I feel as if the ground is moving when I walk and when I stand and sometimes when I sit. I've gone to my GP, my eye doctor, and ENT, and they've all said that they couldn't find anything and it could be anxiety or that I needed an updated glasses perscrpition. I don't know what to do I'm very scared that I might have a brain tumor. Should I go see a neurologist?