I normally get my period very lightly for 2-3 days. i am on day 3 and passed a clot the size of my fist and am now having cramping and bright red blood that soak a tampon every hour for two hours.

See doctor ASAP: Any unexplained vaginal bleeding should be professionally evaluated, and with this amount of blood you should immediately contact your doctor (preferably gynecologist); or visit an urgent care clinic if s/he isn't available. The underlying cause isn't necessarily serious, but the amount of blood loss might be if it continues. Good luck!