If you need to change the sanitary pad / tampon in less than every 2 hour, you should go to ER for the investigations and management. Following can be the causes;
1) Fibroid uterus
2) Uterine polyp
3) Endocervical polyp
4) Hypothyroidism and hyperthyroidism
5) High prolactin
6) Endometrial hyperplasia
7) Other hormonal aberrations
You need to consult your gynecologist as soon as possible for the evaluation and investigations (blood hormonal work up and an ultrasound). Please read the resource;
Please feel free for your follow up questions.
Cancer is quite uncommon in your age group and benign causes are far commoner. As I mentioned, there can be hormonal causes and fibroid uterus (benign causes), which are one of the commoner causes in your age group, responsible for this prolonged and clumpy bleeding. So they should be investigated by the blood work and an ultrasound. A prolonged bleeding of this sort need an earlier look by the physician as it predisposes for the anemia, due to the blood loss.
I hope this was helpful to you. If it was, please remember to ACCEPT the answer so I can get compensated for my work. if you have any more questions, please feel free to ask. I am truly privileged to help you, and I want to make sure that you are satisfied with the answer. Good luck!