You said "change". You mean "new wiring after relay is on"? Can you explain? Voltage reading program should consider the "change"?
After relay is on, the load is equivalent to a resistor "on top of resistor divider". Therefore, the code to calculate the voltage does not work anymore.
can someone suggest a right circuit design?
Based on what I heard so far, I don't exactly what's next step, besides making sure my circuit is wired according to drawing (correct).