Xperia Z keeps shutting down on boot

Hi, before my xperia z used to keep shutting down before, I think it was because my phone was overheating but that was only when I was using apps like youtube and snapchat. Now it shuts down every time. When I turn it on it stays on the sony logo part for around 5 seconds and completely ****s down. I tried re flashing the ftf from flashtool and that still didnt fix it. I also tried using the repair my phone function on pc companion and it still didnt work. I dont know what I did wrong before, im not sure if it was because I unlocked my bootloader and saved my TA partition. Im not sure. But the phone was fine after I unlocked my bootloader. So I cant access the actual phone but I can put it on flashmode and fastboot. Someone help me please.