Y Axis Endstop failing

I just built my first printer. havent manage to print anything yet due to the Y axis endstop.
everything else works fine.
its literally just the Y axis endstop preventing me from homing.

when i home it, it hits the y axis end stop and keeps pushing (causing an auful grinding noise) and i have to abort.

im using a reprap prusa i3.
the y end stop stop is at the back of the machine.
I tried the M119 command, and it confirms the endstop is working. so maybe its my firmware?

any help is appreciated.thanks

The Y End stop is plugged into the min Y endstop plug on the ramps? not the max plug?

I tried switching the plug around (From min slot to max slot). and this still didnt work. However i found a solution

It seems it was a combination of the wrong plug socket and improperly set up firmware.

All working nicely now