Suppose to start period on mon. nothing came. spotting tues-thurs. now heavy flow with extreme cramps. it is usually 3-4 days heavy flow and that's it?

Heavy period: It sounds like you might have had a longer cycle than normal if your days are a little off. It is not unusual for premenopausal women to have heavy bleeding during periods from time to time. The heavy bleeding on average lasts from 2-4 days, and you might pass some larger clots. If the heavy bleeding does not stop after a week, consult your doctor. If this occurs more, treatment may be necessary.