Is it possible to load the css just on my plugin admin page?

To answer the question, from the codex, listed above in the comments.

function load_custom_wp_admin_style($hook) {
        // Load only on ?page=mypluginname
        if($hook != 'toplevel_page_mypluginname') {
                return;
        }
        wp_enqueue_style( 'custom_wp_admin_css', plugins_url('admin-style.css', __FILE__) );
}
add_action( 'admin_enqueue_scripts', 'load_custom_wp_admin_style' );

Note: If you are unsure what your $hook name is .. use this to determine your hookname. Put the code after the { from the function.

wp_die($hook);