eje211

You could do that via mySQL. Something like:

global $wpdb;

$last_day_of_this_month =
    date('d',
        mktime(0, 0, 0,
        the_time('m') + 1,
        0, the_time('Y'))
    );

$this_month_begin =
    the_time('Y') . '-' .
    the_time('m') . '-01';
$this_month_end =
    the_time('Y') . '-' . the_time('m') . '-' .
    $last_day_of_this_month;

$this_month_post_count =
    $wpdb->get_var(
        "SELECT COUNT(*)
        FROM $wpdb->posts
        WHERE post_date BETWEEN this_month_begin AND $this_month_end
        AND post_status = 'publish'"
    );

Though I haven’t tested this.