Plugin Breaking Wordpress Login

Two issues with this plugin, please help...
1 My plugin is breaking my /wp-admin to where all I get is a white screen instead of forwarding to the login screen, which is also broken when this is enabled. The rest of the site works.
2 Another problem with my plugin is that I can't get it to echo back the files in that directory. There are two files in there styles.css and new.css. I've used this method to display files in a folder before but I can't get it to work here.

<?php
 /*
Plugin Name: Call Custom CSS
Description: Call custom CSS files to your theme while still being to recieve theme development updates
Version: 1.1.0
Author: Michele Narup
Author URI: http://michelenarup.com
*/

function addcss(){
$directory = get_site_url() . "/wp-content/css/";
$stylesheets = glob($directory . "*.css");

wp_enqueue_style('styles' , get_site_url(). '/wp-content/css/style.css');
//echo $directory;
    foreach($stylesheets as $stylesheet)
    { 
    echo "<link rel='stylesheet'";
    echo $stylesheet;
    echo "type='text/css' media='all' />";
    }
}
add_action('wp_head', 'addcss');

 ?>

Two issues with this plugin, please help... 1 My plugin is breaking my /wp-admin to where all I get is a white screen instead of forwarding to the login screen, which is also broken when this is enabled. The rest of the site works. 2 Another problem with my plugin is that I can't get it to echo back the files in that directory. There are two files in there styles.css and new.css. I've used this method to display files in a folder before but I can't get it to work here. <?php /* Plugin Name: Call Custom CSS Description: Call custom CSS files to your theme while still being to recieve theme development updates Version: 1.1.0 Author: Michele Narup Author URI: http://michelenarup.com */ function addcss(){ $directory = get_site_url() . "/wp-content/css/"; $stylesheets = glob($directory . "*.css"); wp_enqueue_style('styles' , get_site_url(). '/wp-content/css/style.css'); //echo $directory; foreach($stylesheets as $stylesheet) { echo "<link rel='stylesheet'"; echo $stylesheet; echo "type='text/css' media='all' />"; } } add_action('wp_head', 'addcss'); ?> As per a discussion in the comments below I changed the function to now read:

 /*
Plugin Name: Call Custom CSS
Description: Call custom CSS files to your theme while still being to receive theme development updates
Version: 1.1.0
Author: Michele Narup
Author URI: http://michelenarup.com
*/


function load_my_style () {
wp_register_style('customstyle', get_site_url() . '/wp-content/css/style.css');
wp_enqueue_style('customstyle');
}

add_action('wp_enqueue_scripts', 'load_my_style');

This works but does not fix the white screen problem.  /wp-admin is 
still not rendering anything at all on the page or page source.  Also 
note, problem #2 is now irrelevant based on the new function, I will 
revisit that later. For now I'm focusing on getting the login screen to 
work.