Why can't I stop being hungry?

You can't stop being hungry, because your body need food to work. Your body need food to feed the brain and your body so it can do all it's tasks. Without food you'll have no energy, you can get trouble with your heart and organs.

often we feel we are hungry when we are really thirsty or tired, or body screems for energy while we need to sleep.

If you're a teenager, the likely answer is that you might be going through a growth spurt. That's very likely to make you what seems like unreasonable hungry. However, if you're not, it could be due to doing more exercise, more stress/anxiety than usual, anything that puts your body under more stress than normal. If that is not the case either, then it could just be a phase in your body for no obvious reason. I'm not a doctor or nutritionist, however I have known that to happen to people before. If you think it's a more mental sort of thing, then it's possible your subconscious is using hunger as a sort of coping mechanism.