my sony xperia z1 is not turning on..red led blinks

My sony xperia z1 is not turning on...it's power button was broken last month so i used fastboot to boot into system..:D but suddenly it powered itself off and now i can't power it on using fastboot mode..my pc plays the sound when i connect the phone but sony flashtool doesn't recognize it..when i connect the phone to the pc red led lights up..sometimes while z1 is connected to a charger it turns it self on but after turning on it suddenly dies..please help me to fix this...sorry for bad english:D:D:D