My period is EXTREMELY heavy. HELP?

I'm only 15. I've gone to soooo many doctors and GYN. I use tampons from Tampax Pearl super 2x. these are like bigger than my thumb and index finger combined. I bleed through EVERYTHING. i use those tampons and a thick pad. My tampon lasted me 20 minutes at school and then i changed again TWICE. I ended up going him for the day. I have my periods 24/7 12 months a year. is there any other condition people arent aware about in the world like this? please help me. i'm only 15 years old i shouldnt have this problem. i have tried birth control but it causes breast cancer so NO THANKS. im just so tired of this taking over my life.