Why is my Iphone 4 getting hot and losing battery life?

I've had my Iphone 4 for 9 months. Yesterday while i was at school, I noticed it started to get extremely hot to the point where I couldn't touch it. (It only overheated once.) It was only on twice for a school activity and I sent one message then turned it off. It lost percentage rapidly but due to it being about fully charged I had no idea because i didn't really look at my percentage. I put it to charge last night and this morning I woke up and it only had 10% which is only 8% more than it had been hours ago. I'm getting really scared because I have a lot of pictures, numbers, etc. On there and I don't want to restore it or get a new phone but if i absolutely have to I will. I turned off Wi-Fi and 3G and still nothing. They only way it charges is if it is off but it charges really slowly and loses percent very quickly ( -1% every 45 seconds give or take) Please help! Now it is telling me it is over heated.

Right to start with do a hard reset by holding the home and lock button together for about ten seconds until you see the apple logo appear then release and let the phone boot up.
If this makes no change at all then have you recently downloaded a app that may be causing this to happen? Sometimes it does happen. If so delete the app if this still does not work i would suggest a visit to the most convenient apple store, They will get the phone sorted for you i'm pretty sure.

I hav had that problem it is when it starts to get old

It sounds like there may be something wrong with the battery. First backup everything you have or if its your pics you really want you should be backing them up anyways. Offload all photos and videos from iphone to PC http://www.justtext.com/messageboards/20130202133028.html

Then I would restore to factory and if that doesn't work make an appt at an apple store.

If back of the camera is hot. Just change the camera will be fixed