Question: Is it possible to say Lashon Hara against yourself? If "yes", where is the line between humility and Lashon Hara?
Answer: The "Chafetz Chaim" book says that one should not say Lashon Hara on one's self. He brought a story about himself that once he said Lashon Hara about himself and recieved a few blows for it. Humility hasn't to do with one speaking ill about himself, but with one considering himself void in relation to Hashem.