Get 1 more post in loop

You should probably add a meta query to your WP_Query() args:

$loop = new wp_query(
    array(
        'posts_per_page' => 3,
        // Meta Query
        'meta_query' => array(
            array(
                'key' => 'skip_me',
                'value' => 'true',
                'compare' => '!='
            )
        )
    ) 
);

Or you could perhaps go with the simpler version in this case:

$loop = new wp_query(
    array(
        'posts_per_page' => 3,
        // Meta Query
        'meta_key' => 'skip_me',
        'meta_value' => 'true',
        'meta_compare' => '!='
    ) 
);

In both cases, posts that have the meta value “true” for “skip_me” will not be included in the queried object.