Can anybody let you know that this really is working?
RewriteRule ^update_my_account/([0-9]+)/([0-9]+)/?$ /index.php?page_id=$1&updated=$2 [L]
What area of the URL is $1 and $2 based on?
$1 means first group anything matched up beginning with ([-9]+) inside your rewrite regex and $2 is second ([-9]+).
$1 consists of whatever is matched up through the first expression inside brackets
$2 consists of whatever is matched up through the second