Woocommerce to only run javascript if a specific payment method is selected

I have developed a payment gateway plugin for Woocommerce, and it relies heavily on some javascript which loads a popup to capture user details. I need that javascript to run only if THAT gateway is selected from the radio buttons. For some reason it doesn't work. Here's my code

jQuery(document).ready(function() {
  usingGateway();
  jQuery('form[name="checkout"] input[name="payment_method"]:checked').change(function(){
    usingGateway();
  });
});

function usingGateway(){
    console.log(jQuery("input[name='payment_method']:checked").val());
    if(jQuery('form[name="checkout"] input[name="payment_method"]:checked').val() == 'my_gateway'){
        console.log("Using my gateway");
        //Etc etc
    }else{
         console.log("Not using my gateway. Proceed as usual");
    }
}

It seems woocommerce overrides the javascript in some way, because even though the radio button is selected, my console.log for payment_method is always undefined. Then the IF block is skipped and it always says "Not using my gateway. When I comment out the IF statement, the payment gateway works fine.

But I need it to work because if a user selects another payment method (even BACS or offline payments), the javascript will still load the popup and attempt to process the payment using my custom gateway.

via Chebli Mohamed