Yesterday my iphone 4 started freezing all the time. Not app-specific, but everything, such as safari, mail, etc. Today it got much worse, and I didn't use it for 3 hours while I was in the library, but in that time it went from 90% of the battery to 20%. I go to the library almost every day, and this has never happened, so I know that is unrelated. I rarely ever use more than 50% of the battery in one day. Today I have already emptied the battery twice, while using it very little. It also got very hot today while I was talking on the phone for less than 10 minutes. I haven't changed any settings, installed any new apps, or updated it at all. Any ideas on what's going on?