3 days late, neg hpt, pressure in pelvic area, frequent urination , quesie... what could it be?

Prenancy?: Can repeat pregnancy test in a week with first morning void. 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).