I started charging my phone (with the wall charger) around 12 last night and when I checked it at 10 this morning it was only charged to 40%. After texting a few people, etc. it went down to 30% while still on the charger but after I left it alone it went back to 40%. I turned the phone off and back on and unplugged it from the wall and plugged it back in and nothing's changing. This has never happened to me before. Help!