Default Can't unlock screen

Hi
My mobile is Xperia Go (st27i)
After two or three days that my phone is on, when I try to unlock the screen (by pressing the power key) nothing happen and the screen still remain off,
I should reset the phone (by press power key and volume up)
and after two days the problem come back.
I have flashed many ROMs (including cm11) but I have the problem at all of them.
Please help me to solve this problem.