I just had my period end a week ago and now another one just started. I've always been regular. I've always had very heavy flow. Started period in 04'?

Menorrhagia. Normal menses should be no longer than 7 days and up to 2 days "heavy" with pads change every 4 hours. Longer duration or heavier flow should be evaluated. Your doctor may want to test you for coagulation disorders such as von willebrand's disease.
Thanks for more info. Would still think pregnancy. Can be a miscarriage. Infections less likely. Benign tumors on the uterus are less likely. With your regular periods, it is less likely this is what is called anovulatory bleeding which is most common cause in teenagers, but still could be.