The writer speaks of himself as if he were a worm. This emphasizes that he feels worthless or that the people treat him as if he were worthless. Alternate translation: "But it is like I am a worm and not a man" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Both of these phrase mean basically the same thing. The phrase "despised by the people" can be stated in active form. Alternate translation: "everyone thinks I am worthless and the people hate me" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-activepassive]])