What Causes Feeling Of Imbalance And Head Heaviness

I having a problem since last year i cant stand more than few minuts when i stand then a feeling like imbalance and feelingof fall down and body geting weakness and head heaviness also sometime in legs geting pain too, I consulted a doctor and he said i have BP. After taking medcine for BP now control i.e 120-80 but still i have same problem i cant stand more then geting feeling like imblalance and head heveniness