How to amplify voltage using op-amp
Your schematic will not work, because the voltage polarity in motor can reverse. I suggest use two op-amps as differential amplifier. 

This is the example circuit. With this circuit, for the first op-amp, keep R3 = R4 and R2 = R5, and the output voltage:

\$ \Large V_{out} = \frac{R_5}{R_3} \times V_r \$

For the second op-amp, keep R7 = R8 and R6 = R9, and the output voltage:

\$ \Large V_{out} = \frac{R_9}{R_7} \times V_r \$

Vr is the voltage in R-sense. Vout can not be negative. So you can detect polarity by measuring output voltage of first and second op-amp. In any directions, one op-amp will give voltage near zero, and the other op-amp give voltage measurement of R-sense. 

You can adjust value of R in op-amp to amplify the voltage of R-sense in order to suit the ADC of microcontroller.