Why is my LED blinking?
The beginning of your code in the loop:

void loop()  {
  digitalWrite(ledPin,LOW); //remove this line here
  if (digitalRead(switchPin)==HIGH)
{
     digitalWrite(ledPin,HIGH);//DBG
     delay(500);
}
 if (digitalRead(switchPin)==LOW);
 {
      digitalWrite(ledPin,LOW);//DBG 
       delay(200);
     }
}


Before your first if(digital read(switch pin) == HIGH)  you turn the LED off, and then you have a delay, which gives the blinking effect, remove that and it will not blink.