Light sensor connected to GPIO input of raspberry pi

I have created simple light dector. Schemea is below:

Real circuit on breadboard:

I have written code in python using GPIO library:

import signal
import sys
import RPi.GPIO as GPIO
import sqlite3
import datetime
INPUT_GPIO = 16
def save_light_event_in_db():
    try:
        conn = sqlite3.connect('/home/pi/databases/light_sensor.db')
        cur = conn.cursor()
        cur.execute('SELECT * from light_events')
        light_time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
        message = "Wykryto świt!"
        sqlite_insert_with_param = """INSERT INTO light_events
                              (created_at, message)
                              VALUES (?, ?);"""
        data_tuple = (light_time, message)
        cur.execute(sqlite_insert_with_param, data_tuple)
        conn.commit()
    except Error as e:
            print(e)
    finally:
       if conn:
           conn.close()

def signal_handler(sig, frame):
    GPIO.cleanup()
    sys.exit(0)
def light_detection_callback(channel):
    print("Yeah, juz swita, wstawać!")
    save_light_event_in_db()

if __name__ == '__main__':
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(INPUT_GPIO, GPIO.IN, pull_up_down=GPIO.PUD_UP)
    GPIO.add_event_detect(INPUT_GPIO, GPIO.FALLING, 
            callback=light_detection_callback, bouncetime=1000) 
    signal.signal(signal.SIGINT, signal_handler)
    signal.pause()

This circuit should detect event only when light has turned from night to dawn. I have configured pull up resistor on board. On board I use: GL5539 photoresistor, which has light resistance in range 50-10k, dark resistance 5 mega ohm, 2N3906 PNP transistor.

The problem is, it records also events with twilight. I have checked voltage level on photoresistor and there is 2.63 V in daily light, but when I put my finger on photoresistor, then voltage is rising up to about 3.0 V(small than 0.7 V) and event is detected by input GPIO port. Why? When I takee off my finger, then event is alos detect and that is correct. But first siutation shouldn't be detected. I would be grateful for explanation, some advices. Best regards