Synonyms:
* Confused: bewildered, disoriented, puzzled, perplexed, baffled, uncertain, lost, mixed up, foggy, discombobulated
* (More formal): disconcerted, nonplussed, incomprehensible, unclear, ambiguous
Antonyms:
* Clear: lucid, obvious, understandable, plain, straightforward
* Certain: confident, assured, knowledgeable, informed, decided
* Focused: attentive, concentrated, alert, sharp, composed
The best synonym or antonym to use depends on the specific context of your sentence.