In the passage under discussion, Oedipus expresses his dismay at learning of the crime he has committed, a crime he has committed unwittingly. He has fought against accepting the knowledge of his guilt, but now he has been confronted with incontrovertible evidence that the suspicions raised about his parentage and his crime are true. He is exposed before the world, and he feels shame. In this passage, he details the elements of his crime and the consequences--he has defiled his mother, murdered his father, and offended the gods. He also recognizes that he could not have done otherwise--he is oedipus, and this is his destiny.
The primary conflict in Oedipus Rex is internal and takes place in the character of Oedipus as he fights against recognizing the truth until he is forced to do so. Everything that occurs has been foretold, and yet Oedipus has not recognized that his actions will lead to the consequences the gods have warned will occur. Oedipus's fate is indeed determined before the action of the play, and for that matter it is determined when he is born. His parents are told by the oracle at Delphi that their son would one day kill his father and marry his mother:
They abandon the child, assuming that he has died, but he has not and many years later does kill his father and marry his mother, all without knowing who they are.
Oedipus's fall comes as he learns of what he has done and punishes himself for it. In the Greek view, man is responsible for his actions and must suffer the consequences, though this is difficult to reconcile with the plot of the play because Oedipus's actions are both ordained and undertaken without guilty knowledge. Neither of these factors are considered by the Greeks to reduce his level of guilt, however, and he punishes himself. While he might have exercised more caution in order not to kill anyone who might be his father or to marry any older woman who might be his mother, there is...