CodeIgniter & DBForge - Create Database and Tables

$this->db->query('use db2');

$this->db->query('use DB1');

    if ($this->dbforge->create_database('my_db_test'))
{
    try{
      $current_database = "my_db_test";
      $this->db->database = $current_database;
     $this->db->close();
     $config['hostname'] = "localhost";
     $config['username'] = "root";
     $config['password'] = "";
     $config['database'] = $current_database;
     $config['dbdriver'] = "mysql";
     $config['dbprefix'] = "";
     $config['pconnect'] = FALSE;
     $config['db_debug'] = TRUE;
     $config['cache_on'] = FALSE;
     $config['cachedir'] = "";
     $config['char_set'] = "utf8";
     $config['dbcollat'] = "utf8_general_ci";
     $this->load->database($config);
    $fields = array(
                        'blog_id' => array(
                                                 'type' => 'INT',
                                                 'constraint' => 5,
                                                 'unsigned' => TRUE,
                                                 'auto_increment' => TRUE
                                          ),
                        'blog_title' => array(
                                                 'type' => 'VARCHAR',
                                                 'constraint' => '100',
                                          ),
                        'blog_author' => array(
                                                 'type' =>'VARCHAR',
                                                 'constraint' => '100',
                                                 'default' => 'King of Town',
                                          ),
                        'blog_description' => array(
                                                 'type' => 'TEXT',
                                                 'null' => TRUE,
                                          ),
                );

    $this->dbforge->add_field($fields);
    $this->dbforge->add_key('blog_id', TRUE);
    $this->dbforge->create_table('ipn_log', TRUE);
    }catch(Exception $e){
    echo $e->getMessage();die;
   }
  }

}