Sorry to hear this but in circumstances like this the best advice we can give is for you to return your device to the place of purchase or contact Xperia care to have your device inspected http://www.sonymobile.com/gb/support/contact-us/
You could try performing a system repair but I'm not sure this will work given the circumstances you have however if successful then this will factory reset your phone
Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds)
Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the onscreen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process
If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP
