Ok, the causes of heavy periods include endometriosis, ovarian cysts, cervical polyp, pelvic inflammatory disease (PID), STDs, bacterial infections, and rarely, cancers.
To find out the exact cause, a pelvic exam, ultrasound, and some blood tests to check the thyroid (free T4 and TSH) are done.
If all this has been done, then you should discuss some options to reduce bleeding.
This could be a hormone-releasing IUD, like Mirena.
Or birth control pills, including continuous pills like Seasonale, where you have a period once every three months.
I hope this helps?
Please let me know if you have any questions about this.