Hi Tali,
I hope this doesn't sound insensitive but could he be learning this behaviour as a coping mechanism? The reason I ask is that in the original post where you say that he hates himself, you pretty much say the same kind of thing about yourself.
Is this something you say out loud about yourself when things go wrong? If it is, perhaps you could look inside yourself and think about why you say it (eg. do you really think that? does it get you attention you feel you don't get otherwise? do you easily blame yourself?). Perhaps if it is learnt then he is responding to the same triggers.
As I said, I am sorry if this seems out of line, because I don't know you or your son, but wanted to point this out as a possibility because it is obviously an important issue to sort out now for your son.