I seemed to have lost all soul or sensation
The terms become starker and starker, now directly figured as beyond Victor's control, the operations of a destiny in which he is a mere pawn. Moreover, this force, however much it may be involved in creation, is on a personal level destructive. As Victor nears success in his endeavor to create life, it is as if the process directly saps his own vitality.
Perhaps, however, there is an alternate, less dire, way of reading this condition, as reflecting Mary Shelley's own experience with motherhood. On some preconscious mental level, Victor is shown to be replicating the experience of the expectant mother whose physical being is strongly affected by the second being gestating in her womb.