There are hints in the book that Harry's emotions were being manipulated. When he was studying with Snape, at one point he fell asleep while reading a book. The passage he was reading referred to a potion that can inflame your emotions, making them harder to control. Then Harry fell asleep and never pursued the thought.
That sounds an awful lot like what Harry has been going through, so I think it's possible that someone has been slipping Harry that potion.
That sounds an awful lot like what Harry has been going through, so I think it's possible that someone has been slipping Harry that potion.