This code I put together to add extra info in after someone has already registered... Can you find the simple mistake or huge mistake, of which I do not know?

<?php
echo "<h1>Create a Cat</h1>";

include("connect.php");

$username = $_SESSION['username'];

$submit = $_POST['submit'];

//form data
$cat1name = strip_tags($_POST['cat1name']);
$cat1gender = strip_tags($_POST['cat1gender']);
$cat1bio = strip_tags($_POST['cat1bio']);
$cat1mate = strip_tags($_POST['cat1mate']);


if ($username)
{

echo "Come to create a cat, ".$username."?<br/>";

if ($submit)
{

//create a cat!!!

$query = mysql_query("

INSERT INTO users VALUES ('','','','','','','','','$cat1name','','$cat1gend er','$cat1bio','cat1mate') WHERE username='$username'

");

die("<a href='cat1pic.php'>Upload it's picture</a>");

}

}
else
die("You must be logged in!");

?>

<br/>

<html>
<form action='createcat1.php' method='POST'>
<table>

<tr>
<td>
Cat's Name:
</td>
<td>
<input type='text' name='cat1name'>
</td>
</tr>

<tr>
<td>
Cat's Gender:
</td>
<td>
<select name='cat1gender'>
<option>She-cat</option>
<option>Tom</option>
</select>
</td>
</tr>

<tr>
<td>
Cat's Bio:
</td>
<td>
<input type='text' name='cat1bio'>
</td>
</tr>

<tr>
<td>
Cat's Mate:
</td>
<td>
<input type='text' name='cat1mate'>
</td>
</tr>

</table>
<br/>
<input type='submit' name='submit' value='Create a Cat!'>
</form>

</html>