I think it is probably lack of blood flow to your brain. I would suggest taking the Omegas which is in Fish Oil supplements. You should also make sure you are breathing correctly and take deep breaths here and there to assure the oxygen flow. Drink plenty of water to stay hydrated. Exercise will also help circulation for the brain. You might also want to take iron along with the fish oil because usually Anemia as your doctor probably told you is an iron deficiency. Get blood tests from your doctor too if you haven't already. Best of luck to you!
Have you checked for gas leaks? are you near a washer, dryer or boiler?
Your iron levels could be off or you could be having vertigo which is a symptom of other illnesses. You should keep a diary of everything in detail. What you ate when you use the bath room when you sleep and wake up and what sensations or symptoms you have that aren't normal to you. Bring that in to the doctor and have them look at it because the more in depth they know the better they can pick the right tests. If they don't know much they will go for basic. best wishes