Samsung Galxy Note battery SERIOUSLY DRAINS OUT in MINUTES?!!!?

I think it has got to do with me overcharging cos I turn on my charger every night... But now the battery life suddenly falls within minutes when I remove my ohone from the charger, even when the battery on the screen appears 3/4 full. And right before it runs out the screen will start flickering and then it dies.. The only way i can use it is if I charge and use at the samee time T.T Does anyone know how to fix this problem? Like do I need to change the battery?