Well, without a detailed clinical evaluation it would be difficult to determine the cause of your symptoms. With normal radiological/ neurological tests, possibilities that may need to be considered include low blood sugar, low/ high blood pressure, micronutrient deficiencies, hormonal/ endocrine issues, stress/ anxiety, cardiovascular causes, autonomic disturbances, peripheral neuropathy, heavy metal poisoning etc. I would suggest considering a detailed evaluation by an internist initially and depending on the cause diagnosed/ suspected, it can be managed accordingly or specialist care may be sought.
Hope this is helpful.
I have similar symptoms as you except I also have depersonalization and leg fasciculations and a hard lump in the back of my neck. I have done all the tests you mentioned (except spinal tap) +blood sugar + micro nutrients +Heart CT for CAD +abdominal scans +repeated Lyme disease tests +thyroid and parathyroid ultra sound and PET scans and dozens blood and urine tests. I have been to internists, neurologists, ENTs, a psychiatrist and even a neurosurgeon and a sleep disorder specialist to make sure I didn't exclude anything. Along the way they found a chlamydiae pneumonia infection, thyroid nodules, a potential pericarditis, hypercalcemia and extremely low levels of vitamin D.
I have now been diagnosed with potential idiopathic early hyperparathyroidism but according to the doctor that doesn't explain the loss of balance, dizziness and leg fasciculations so I decided to put that under stress/anxiety which it could very well be after all.
Have you been under severe stress lately? Are you a naturally anxious person? It's a good thing all your tests turned out normal so far. So don't be too worried about your symptoms. If I were you I would go to an internist for a thorough evaluation as suggested by Dr Kaul. That's personally what helped me the most!