Soucis avec mon script

<?php include ('../inc/header.php'); ?>
<?php 
	if (isset($_SESSION['prenom']) && isset($_SESSION['nom']) && isset($_SESSION['pseudo'])) 
	{
		header('Location: profil.php');
	}
	else
	{
		if(isset($_POST['login']))
		{
			if($_POST['pseudo'] == NULL OR $_POST['pass'] == NULL)
			{
				echo 'Tout les champs doivent être remplis !';
			}
			else
			{
			$pseudo = htmlspecialchars($_POST['pseudo']);
			$pass = htmlspecialchars($_POST['pass']);
			$ip = $_SERVER['REMOTE_ADDR'];
			
			$req = $bdd->prepare("SELECT * FROM account WHERE pseudo = :pseudo AND pass = :pass");
			$req->execute(array('pseudo' => $pseudo, 'pass' => $pass));
			while ($donnees = $req->fetch())
			{
				$sql = $donnees->rowCount();
				
				if($sql > 0)
				{
					session_start();
					$_SESSION['prenom'] = $donnees['prenom'];
					$_SESSION['nom'] = $donnees['nom'];
					$_SESSION['pseudo'] = $donnees['pseudo'];
					$_SESSION['ip'] = $ip;
					header('Location: accueil.php');
				}
				else
				{
					echo 'Nom de compte ou mot de passe incorrect !';
				}
			}
			}			
		}
		else
		{
			header('Location: login.php');
		}
$req->closeCursor();		
	}	
?>	
<?php include ('../inc/footer.php'); ?>