memory issue in Removing an external swf from stage

programming flash
1

I had 28 swf files, which are connected with a main swf, and the main swf is loaded external to a blank swf.
On the main swf there a 26 buttons which are linked to 26 swf and each 26 swf have a back button which will return to the main swf.
All are working fine accept the memory issue. Please help me with this

The script I used in the main swf to go to the other 26 swf is

var loader_mc : Loader = new  Loader();
   addChild(loader_mc);

btn_main_apple.addEventListener(MouseEvent.CLICK,  buttonClick)
function  buttonClick(e:MouseEvent):void
{
     try{
loader_mc.unloadAndStop();
} catch(e:Error) {
}
      var urlRequest : URLRequest = new  URLRequest("FitzroySound_A.swf");
      loader_mc.load(urlRequest);
}   


btn_main_bird.addEventListener(MouseEvent.CLICK,  buttonClick2bird)
function  buttonClick2bird(e:MouseEvent):void
{
     try{
loader_mc.unloadAndStop();
} catch(e:Error) {
}
      var urlRequest : URLRequest = new  URLRequest("FitzroySound_B.swf");
      loader_mc.load(urlRequest);
}

btn_main_cat.addEventListener(MouseEvent.CLICK,  buttonClickCat)
function  buttonClickCat(e:MouseEvent):void
{
     try{
loader_mc.unloadAndStop();
} catch(e:Error) {
}
      var urlRequest : URLRequest = new  URLRequest("FitzroySound_C.swf");
      loader_mc.load(urlRequest);
}

and so on…

And the script I used on the other 26 swf to return to the main swf is

var loader_mc : Loader = new  Loader();
addChild(loader_mc);


logout_btn_drw_z.addEventListener(MouseEvent.CLICK,  buttonClick)
function  buttonClick(e:MouseEvent):void
{
     try{
loader_mc.unloadAndStop();
} catch(e:Error) {
}
      var urlRequest : URLRequest = new  URLRequest("FitzroySound_mainScreen.swf");
      loader_mc.load(urlRequest);
}

Please help me