Let it run completely out of battery, remove the battery, let it cool, then put the battery back in, and let it charge completely before turning it back on. Limit your Data and Wi-Fi usage off-charger. If you see the battery plummeting, you need to put it on Airplane Mode immediately. Airplane Mode also helps charge the phone back up faster. If you feel your phone overheating, you need to stop using it until it cools. Taking off the back and any covers speeds up the cooling. I know this from personal experience. You might consider getting a new phone very soon. I suggest the S4 Active. (Waterproof up to a meter for 30 minutes)