how can i display all youtube videos from a users youtube account

You can use YouTube developer API. Example how to get recent videos below:

$data = wp_remote_get('http://gdata.youtube.com/feeds/api/users/<USERNAME>/uploads/?start-index=1&max-results=40');
$response =  new SimpleXMLElement($data['body']);

foreach ($response->entry as $entry):
    $vid_id = '';
    if ( preg_match('#videos/([^/]+)$#', $entry->id, $matches) ) {
        $vid_id = $matches[1];
    }
    if ( $vid_id ):
    ?>
        <a href="http://youtube.com/watch?v=<?php echo $vid_id; ?>">
            <img src="http://i.ytimg.com/vi/<?php echo $vid_id; ?>/1.jpg" width="220" height="130" />
            <span class="video-title"><?php echo esc_html($entry->title); ?></span>
            <span class="video-description"><?php echo esc_html($entry->content); ?></span>
        </a>
<?php
    endif;
endforeach;