The phrase "am on the back of" suggests an action of being in control or leading from behind. The antonyms for this phrase could be "am in front of," "am leading," "am at the forefront," or "am in charge." These antonyms imply a sense of authority and taking charge, rather than following from behind. Additionally, antonyms could include "am lost," "am confused," or "am unsure," which portray a lack of direction or control. Ultimately, the antonyms for "am on the back of" refer to a different status or position, where one is not necessarily behind, but rather in front or in charge.