After Hedwig, he never got a new owl. She wasn't his familiar, but she was his friend and as muggles would call her his pet. The goblins told him about how she couldn't have formed a familiar bond with him and he was devastated. It was too much for him to handle. Not only did he find out how Ginny and Molly potioned him for years, he also found out how Dumbledore had bound Harry's magical core and intended for him to die. He was influenced by so many compulsion charms, loyalty hexes, jealousy jinxes, as well as love, hate and lust potions that he didn't know how he was able to defeat Voldemort at all. 