Simple op-amp differential amplifier
Your circuit is wrong.  You can't expect the output to swing negative when the supply is 0V and +5V.  Opamps don't generate negative voltages on their own.  

Option 1:  Fix your supply.  Supply the opamp with -5V and +5V.

Option 2:  Arrange for the output to swing around +2.5V instead of ground.  For example you could split R3 into two 2kΩ resistors.  Connect one to ground and one to +5V.  This generates a 2.5V supply with 1kΩ Thévenin impedance.