IPhone 4 - Won't hold charge, very very hot to touch?

Most of the time, it won't charge at all. I'll plug it in for hours and it'll stay dead. I've tried 4 different plugs, 2 different USB adapters, 3 different computers' USB ports and multiple home outlets.

It finally charged today to 100% but within 2 hours, it's down to 20%. I got 3 texts in that time, but otherwise, haven't used it at all. It's extremely hot to the touch. It got hot when I had it plugged in before and it wasn't charging, too.

I've double-tapped the home button and closed All open apps and it's still doing this.

Please help! I need my phone for GPS on Friday cause I'm going on a trip and don't really know where I'm going.

Change the case.

Sometimes the case makes it overheat. Try restarting it too. Also, check where you leave it. If you leave it somewhere where it would get warm (in the sun, in a bundle of blankets, etc) that will not help.

if worst comes to worst, you will need to delete some of the apps you have to create more storage.
if you can, take it to apple and see if it needs a new battery. Sometimes the battery loses its charge and becomes unstable and can overheat, melt your phone, or damage your phone.