Why isn't my login system working?

For whatever reason, i can't get my login system to work.  i figure it has something to do with cookies or whatnot. yes i know that this code leaves me open to injection attacks & my password isn't hashed, but this is just for testing it at the moment (and i've got no idea how to protect against injections)

in any case, this is my code

if(isset($_COOKIE['ID_my_site']))
{
      if ('ID_my_site')
      //if there is, it logs you in and directes you to the members page
      {
            $username = $_COOKIE['ID_my_site'];
            $pass = $_COOKIE['Key_my_site'];
            
            $check = mysql_query("SELECT * FROM users WHERE username = '$username'");
                        
            while($info = mysql_fetch_array( $check ))
            {
                  if ($pass != $info['password'])
                  {
                        echo("wrong password");
                  }
            }
      }
}
//IF FORM HAS BEEN SUBMITTED
if (isset($_POST['submit']))
{
      if(!$_POST['username'] | !$_POST['pass'])
      {
            //die('You did not fill in a required field.');
      }

      $check = mysql_query("SELECT * FROM users WHERE username = '".$_POST['username']."'")or die(mysql_error());

      $check2 = mysql_num_rows($check);
      if ($check2 == 0)
      {
            die('check2 is zero!!!<a href=index.php><br> Try again</a>');
      }

      while($info = mysql_fetch_array( $check ))
      {
            $_POST['pass'] = stripslashes($_POST['pass']);
            $info['password'] = stripslashes($info['password']);            
            $_POST['pass'] = ($_POST['pass']);
            
            //gives error if the password is wrong
            if ($_POST['pass'] != $info['password'])
            {
                  //die('Incorrect password, please try again.');
                  die('password wrong 2!!!<a href=index.php><br>Try again</a>');
            }
      
            else
            {
                  // if login is ok then we add a cookie
                  ob_start();
                  $username = stripslashes($_POST['username']);
                  $pass = stripslashes($_POST['pass']);
                  $hour = time() + 3600;
                  setcookie('ID_my_site', $username, $hour,"/db/","www.prospect-select.com",false);
                  setcookie('Key_my_site', $pass, $hour,"/db/","www.prospect-select.com",false);
                  header("Location: index.php");
                  ob_end_flush();                  
      }
            

      }
}
//IF USER HASN'T SUBMITTED FORM
else
{
      //just displays a login form, which when submitted runs through the checking at the top of the code snippet
}

this is the login check placed on every page

ob_start();
include ("config.php");

if(isset($_COOKIE['ID_my_site']))
{
      $username = $_COOKIE['ID_my_site'];
      $pass = $_COOKIE['Key_my_site'];
      $check = mysql_query("SELECT * FROM users WHERE username = '$username'")or die(mysql_error());
      while($info = mysql_fetch_array( $check ))
      {
            if ($pass != $info['password'])
            {
                  header("Location: login.php");
            }
      }
}

else
{
      header("Location: login.php");
}

ob_end_clean();

problem here is that i'll login using a valid password, and it won't log me in, i'm 99% sure theres a problem setting cookies

thanks in advanceStart Free Trial