See a doctor, periods this heavy can be a sign of some underlying issue. It could also be causing issues, such as anaemia. They may encourage you to go on the pill, but I would encourage you to try and get them to look into it, as hormonal contraception may cover up the problem, but they won't diagnose or solve an existing one.
Around 80% of people who switch to using reusable menstrual products (menstrual cups, cloth pads and tampons and natural sponge tampons) find that their period gets lighter and shorter. They also tend to hold a fair amount more than disposables. We don't know why it happens, but best guess its to do with getting rid of the chemicals found in disposables. As I said, see your doctor, but its something to think about.