I have no screen protector, the cell is clean and quite new. I tried xperia disgnostic and it tell me the proximity sensor is always detecting something. I tried calibrating the sensor with *#*#7378423#*#* but the ability to calibrate is not present only the testing. According to sony pc companion i have the latest version. I just resetted my phone to make sure it was not the problem.
Build Number: 14.3.A.0.757