Suggest Treatment For Irregular Periods

I was just wondering why my period is lasting so longer than usual? Some times I have it and some months I don't. I didn't know if that had anything to do with it or not, but I don't ever remember being on my peroiod for this long, but actually I think its only been close to a week and other times it seems like it will only last for about 3 or 4 days!