I have been on my period for three weeks and tried taking a birth control pill to altar it. and nothing has changed. should i be worried?

Probably Not: You need to stabilize the linig of the uterus to stop the period. Either by stabilizing with more estrogen, or by completely starting fresh with first starting and then stopping a dose of progesterone. It can also have nothing to do with your uterus at all. Diabetes and thyroid disease as anemia can also be suspect. See your doctor!