I got my period the same day i started chlamydia meds, after having a somewhat late period. this was in sept and i'm now 16 days late. is this normal?

Not sure of reason.: Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives & other meds, Illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., PCOS). Pregnancy is #1 reason.