My period was due yesterday, i was crampy all week. now the cramping has gone away completely and still no period. what should i do?

If sexually active -: Take pregnancy test. Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders, anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems. #1 reason is pregnancy. See dr if no period x 3 cycles (or sooner of sign sxs.).