2nd header not directing to thank_you page

Hi there, I am trying to re-direct users to a thank you page.  But I get a header error because the code thinks that I have already sent a header as part of session variables and as such, cannot create another.  Can someone help me with this problem?

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err
====
Warning: Cannot add header information - headers already sent by (output started at /home/4435/pebbles/www.sixoone.com/public_html/biz/dev/add_card2.php:22) in /home/4435/pebbles/www.sixoone.com/public_html/biz/dev/add_card2.php on line 109

code
===

<?php
session_name();
session_start("first_name");
session_start("last_name");
session_start("cust_num");
session_start("username");
session_start("email");
if ((!(session_is_registered("first_name")))||
    (!(session_is_registered("last_name")))||
     (!(session_is_registered("cust_num")))||
     (!(session_is_registered("username")))||
     (!(session_is_registered("email"))))
{
session_unset();
session_destroy();
$url = "Location: re_userlogin.php";
header($url);     -------- header 1
}
else
{
echo "<b>Hello $first_name $last_name, you are Customer No. $cust_num, you are logged
in.</b>";
}
?>
<?php
//brians code start here
include "functions.inc.php";
include "error_messages.inc.php";

//action=add means usr pressd the submit button
if ($action =="add")
{
 $error_found=false;
 $error="";
 //start validating the user input
 }
 if($co_name=="")
 {
  $error_found=true;
  $error.=ERR_CO_NAME_BLANK;
 }
 if($inda=="")
 {
  $error_found=true;
  $error.=ERR_INDUSTRY_BLANK;
 }
 if($position=="")
 {
  $error_found=true;
  $error.=ERR_POSITION_BLANK;
 }
  if($equip=="")
 {
  $error_found=true;
  $error.=ERR_EQUIP_BLANK;
 }
if(!$error_found)
{
 $db_name = "afa";
$table_name = "_089";
$connection = @mysql_connect("mysql", "ps", "nro") or die("Couldn't connect.");
$db = @mysql_select_db($db_name, $connection) or die("Couldn't select database.");
$sql = "insert into $table_name(
       email,
         co_name,
         inda,
         other,
         url,
         position,
         hours,
         cost,
         equip,
         web_source,
         username,
         cust_num,
         agent,
         status,
         date_reg,
         type)
         values(
             \"$email\",
             \"$co_name\",
             \"$inda\",
             \"$other\",
             \"$url\",
             \"$position\",
             \"Open all year Round\",
             \"Available on Request\",
             \"$equip\",
             \"bizafrican\",
             \"$username\",
             \"$cust_num\",
            129,
             \"active\",
             curdate(),
             \"client\")";
$result = mysql_query($sql,$connection);
$sql1 = "update _089 set inda = \"089\" where inda = \"_089\" ";
$result1 = mysql_query($sql1,$connection);

Header("Location: do_089xx.php");  -------- header 2  -- not working
exit;
}
else
{
 $error=ERR_HEADER.$error;
}
?>