As explained by others, incremental encoder (possibly in combination with limit switches) is the usual way to monitor stepper motor movement. sairfan1 has suggested a feasible method to implement it without dedicated interrupt inputs in post #4. In so far I think, this part of the question can be considered as solved.
If you prefer though to use an analog position monitoring method (potentiometer, analog hall sensor, whatsoever), you'll need to add it to your drive design.