Every time, the value of the flex sensor reduces by 5k I want a dc geared motor to spin for .5 sec and for every 5k increase, it must pin in anti clock wise directioni for .5 sec.
This specifies specific durations for the motors to spin.
What I really want my motor to do is to rotate as the analog values drop from 225 to 103.
This specifies conditions to start and stop the spinning.
The requirements are completely different, and non-inclusive.
Which do you really want to do? What is the purpose of spinning the motor one way or the other?
Perhaps you have chosen the wrong kind of motor. It almost seems like a servo or stepper motor would have been a better choice.