account for othellos confidence in his responce to the fearsthat iago has about his safety and hi we'll being

I'm not quite sure if you are referring to a specific line in the book. Iago drops not so subtle hints that he worries about Othello's well being throughout the play. I think as a general rule, Othello is rather bi-polar. He either puts on a strong manly front or he is terrified by his thoughts and fears. Earlier in the play, Othello shows certainty in all aspects of his life. He feels that he is venerated and needed by the state and his wife. He also thinks he is quite "the man", rebuking any insinuations that he may be driven to less, "But I do love thee! and when I love thee not, Chaos is come again."