If you feel weekness all the time then you must go for check up with a doctor. Weekness is due to lackness of iron, calcium, vitamin D and many other vitamins. You should consult first with your doctor then follow the doctor's advice. Moreover I would suggest you should add healthy food in your diet like add green vegetables, fresh fruits, salad, milk, curd,dryfruits etc. Take some time for exercise or yoga. Wake up early in the morning and take sleep atleast 8 hours. Drink 2 to 3 liters of water in a day. Eats small meals every after 2 hours and avoid junk food like maida, packed food etc.