Are you charging it with the regular charger? Because I used to charge mine with the iPad charger (thinking they were exactly the same). The iPad charger is stronger so it may be able to cause problems like yours.
The problem could be caused by the design of the iPhone. Try to remove the back cover while charging. Alternatively, try to update to the latest version of ios. If these still does not help, your battery nay have fried.
Hi, A, My iPad has been getting really hot lately too! That's why I'm not on it much! I refuse to charge it at night anymore! I used to let it charge all night but, all of a sudden it started getting real hot! I'm using my iPad charger so I don't know! I haven't forgotten you, friend! It's been rough, you know what I mean! P.