Recently, my iPhone 3G has become extremely slow. It freezes at random times, sometimes it takes over 30 seconds to start playing a song. App loading times are also very slow. Along with the slowness, my battery life has become terrible. My phone used to last me the whole day, but now the battery can run dry after just a few hours of use. For example today I've used it for 2 hours, most of that music listening, and now my battery is at 50%. What should I do?