The phrase "am at bottom of" implies being at the very bottom or foundation of something. Antonyms for this phrase could be "on top of," "at the surface," or "at the pinnacle." These words convey the opposite idea of being grounded or foundational, instead representing a sense of height or achievement. Synonyms for "am at bottom of" could include "am the foundation of," "am the basis of," or "am the core of." Depending on the context, different antonyms or synonyms could be more appropriate to convey the intended meaning.