I would have to agree that it's probably hormonal in your case, tho there are lots of theories about acne.
However, Chinese medicine says that chin Acne is testosterone-induced. I found that the all-natural supplement called saw palmetto helps balance testosterone. Also, there is a topical lotion that contains estrogen and progesterone (which also balances testosterone) called Jan Marini's transformation serum (google to get it) that works better than ANY of the drugstore/prescr*iption junk.
Beware the Antibiotics ...being on them promotes Candida, which can make Acne worse so you end up needing more Antibiotics . It becomes a vicious cycle.