On april 19th i had my period for one day and then i had unprotected sex and i spotted 2 days ago when i was supposed to get my period

Irregular menses.: 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.