My period was late and last night from 8 till 12 i had heavy cramps and the my period started wat was bright red and watery but nou it seems to go away buy the cramps still here what can it be?

Menstrual cramps ?'s: A "late onset" of your period may be secondary to temporary blockage of normal bleeding due to clot formation which blocks the passage of blood until the clot is dissolved, followed by a sudden rush of blood. If pregnancy is possible, get a serum HCG test to be certain about pregnancy, especially of pregnancy outside the uterus (ectopic), which needs immediate attention.