[Q] Pc connection problem (E 975) topic

hi .. I have lg optimus g E975 running kitkat ( not rooted ) it was working good but now when i try to connect it to any pc by cable it feels that a charger and the pc doesn't feel any connection i know there is pc connection setting in setting menu i tried every thing . i made factory reset from setting menu and hard reset all that doesn't work .. i opened the hidden menu and tried every thing about usb connection and the same problem exists .. and of course i tried different cables ...
plz help :(
notice that last time it was working the touch wasn't responding good when it was connecting to pc