Here "bitterness" represents suffering. It is referred to as if it were something that could fill the speaker. Alternate translation: "He has caused me to suffer very much" (See: [[rc://en/ta/man/jit/figs-metaphor]])
Wormwood is the bitter juice from the leaves and flowers of a certain plant. Drinking that bitter juice represents suffering. Alternate translation: "it is as though he forced me to drink something very bitter" (See: [[rc://en/ta/man/jit/figs-metaphor]])