my sony mp3 walkman just turns on and shuts right back off?

my mp3 turns on and shuts right back off, when i plug it into a computer it takes forever for the computer to read it, then when it actualy reads it, my mp3 thinks that the battery is full when it's not, whwen it plug it into the wall., it doesnt turn on its stuck in loading mode, i have fixt this problem before by pluggin it into a wall, but this time it doesnt work. what should i do?