Android not detecting USB though it is connected

I am using YU YUREKA that runs on Cyanogenmod 11.0 with Android 4.4.4. Suddenly I found that my device is not detecting the USB connection. Though my phone is getting charged, it shows 'USB not connected' in the tethering option. I have checked that with different computers and USB cables but without use. Later I go to Settings > Developers options > Android debugging and enable the Android Debug Bridge (adb). Then my device starts to detect the USB. But when I turn off the Developers option, again it stops detecting the connection. If anyone could help me in this matter. Also is it safe to use tethered data connection with debugging mode turned on?