We'll introduce some expressions regarding pain.
When you have a pain, you say ~ga itai desu meaning "~ is aching." For example, "tooth" is ha, so if you have a toothache you say ha ga itai desu—"my tooth is aching." And "head" is atama, so "my head is aching" is atama ga itai desu.
Many Japanese families are equipped with a clinical thermometer and if they're not feeling well, people first take their temperature. Providing accurate information such as when and by how much your temperature has risen helps a doctor to give a correct diagnosis. It's always useful in the event of an emergency if you know your normal temperature.
