Period

I had my period for 3 and a half weeks and then didn't get it for three months, now I have it and it is super heavy and I bleed through a heavy tampon every 10 minutes. Also every time i get my period I get the worst cramps in the world and all I can do is lay in bed and nothing helps. Also I got my period when u was eight, any ideas in what it could be. I've had my period for 8 years so it's not just " trying to figure itself out"

Please comment anything that it could possibly be