Period a few days late & yesterday had light spotting. ive been fatigued, had cramps & nausea. hpt was negative today. pregnant or something else?

You can retake HPT: in a week. 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.