just to add to what everyone else is saying, it would be worth taking vitamin tablets, in particular iron supplements.
As you have been loosing blood for so long you, there is a good chance you are anemic, (which the iron tablets would fix) and you could be low in a lot of other vitamins as you are loosing so much blood.
And you definitely need to see a doctor to stop the bleeding.
Fifteen days of this type of period is unusual. Yes, absolutely go see your doctor to determine what is going on. good luck dear and let us know what the outcome is!
My advice is that you should go and see your doctor.
It is not normal to bleed for so long and to have large clotting.
The doctor can give you medication, send you for an ultrasound to find out what is causing these heavy bleeds, and possibly do blood tests to check your blood for iron deficiency and a hormone imbalance.
Make an appointment with the doctor so that he can help you with this.
Best wishes.