Honestly, I would be expecting you to have more symptoms, and certainly more debilitating ones, if you had cancer in the brain. What you are describing sounds very much like what I experience when my sinuses flair up. I feel like I'm really struggling to keep my balance, yet I seem to have no physical difficulty in doing so. I can walk five miles, navigate the stairs, walk in a straight line with no difficulty. It just feels like everything is moving, and that I'm going to fall. That causes anxiety of course, which then makes everything ten times worse.