I get my period every week and a half and it lasts for a full five days. what could this be?

Time to see your doc: Without knowing any symptoms, or further info, this needs to be seen by your ob/gyn, who can do further work up, and testing for possible fibroids or other causes, and to make sure you aren't anemic from all that blood loss through your increased periods/month. Don't delay! your life is precious. They will know exactly what to do.