Help My REGEX isn't working

Here is my code

$dataOK=TRUE;
//enter rows into database
foreach($_POST['Activity'] as $row=>$Act)
{
if (!empty($_POST['Activity'][$row]))
{ 

  $Activity=($Act);
  if(!empty($_POST['Activity'][$row]) && !ctype_alpha($_POST['Activity'][$row]))
  {echo '<b>One of your Activity columns is not in the proper format. Make Sure it is a word<br/>';$dataOK=FALSE;}
  
  $Position=($_POST['Position'][$row]);
  if (!empty($_POST['Position'][$row]) && !ctype_alpha($_POST['Position'][$row]))
  {echo '<b>One of your Position columns is not in the proper format. Make sure it is a word.<br/>';$dataOK=FALSE;}
  
  $StartDate=($_POST['StartDate'][$row]);
  if 
  (!empty($_POST['StartDate'][$row]) && !preg_match('/^(0[1-9]|1[0-2])-(19|20)\d{2}$/',$_POST['Startdate'][$row]))
  {echo '<b>One of your Start Date columns is not in the proper format. Make Sure it is MM-YYYY<br/>';$dataOK=FALSE;}
  
  $EndDate=($_POST['EndDate'][$row]);
  if (!empty($_POST['EndDate'][$row]) && !preg_match('/^(0[1-9]|1[0-2])-(19|20)\d{2}$/',$_POST['Startdate'][$row]))
  {echo '<b>One of your End Date columns is not in the proper format. Make Sure it is MM-YYYY<br/>';$dataOK=FALSE;}
  
  
  if($dataOK && !empty($_POST['Activity'][$row]) && !empty($_POST['Position'][$row])&& !empty($_POST['StartDate'][$row]) && empty($_POST['EndDate'][$row]) )
  {

  $involv = "INSERT INTO Involvement (Activity, Position, StartDate, EndDate,ULVID)
  VALUES ('$Activity','$Position','$StartDate','$EndDate','$ULVID')";
  }
   
 

  if (!mysql_query($involv,$con))
{
    die('Error: ' . mysql_error());
  }
  echo "Record Added<br/>";
  }
}

Code (markup):

Even if i put in a correct date format the parser is telling me that it's wrong. Can you see anything I messed up on? the date is supposed to be in MM-YYYY format.

Thankyou in advanced

 

Why are you making a new thread, you already made a thread for this if I remember correctly.