lightheadedness often comes from stress, nobody seems to know exactly what causes it though, did any doc explain what actually happens to cause it?
quinine can cause it as a side effect

smelling salts can stop it for a while, so can squeezing something sharp in hand and concentrating on the pain

sounds like you need to learn relaxation, perhaps meditition and stress reduction methods, also try gentle exercise, long walks, jacuzzi spa baths, massage, etc