Hello, You are just above the average weight of your height. Your child is 8 months old, breast feeding. Any mother while breast feeding needs extra calories. Some mother drastically cuts down their diet intake to reduce pre partum weight gain. Intake should be as per the need. So intake should meet your routine work as well as the baby s need. So a healthy diet with moderate exercise is preferable. Eating small meals with healthy snacks in between (pregnancy advised diet) is preferable. Balanced diet should contain Carbohydrate, proteins, fats, Vitamins and mineral. Supplement of vitamins, minerals and calcium is allowed. Except fish all other non Vegetarians are high in fat leading to high cholesterol, which is of no use. Your diet should contain more of proteins with lesser amount of carbohydrate and very minimum amount of fat and richer amount of vitamins and minerals (green vegetable food). All these things will take care of your tiredness and pain. But you have to watch for any other cause is present for pain. Breast feeding, sitting in a particular position without movement also can cause pain in the back and neck. Wearing abdominal belt to regain the lost tone of the abdominal muscles is also important. I hope you understand With best wishes