Oh OP, you have my sympathies! Mine never lasted quite that long, but when I was first into peri, oh god it was awful. How old are you, are you perimenopausal? Have they ruled out things like fibroids, endometriosis?
First off, if you're not taking iron, make sure you do, your iron stores will be very depleted. I have read that if that happens then you can actually bleed harder and longer, though I've no idea of the science behind that.
If you dont have anything like fibroids and aren't heading into menopause, it could be that your hormones are 'imbalanced'. I found that if I 'controlled' my estrogen then bleeding was less heavy and long. The idea of being 'estrogen dominant' is debated, but if your estrogen is 'higher' relative to your progesterone levels, it can cause heavy bleeding. I took a supplement called 'DIM' (acronym for something I can't spell) and it really helped. I also believe it stopped the growth of a small fibroid that I had. I also used a natural progesterone cream for a while, and it made my cycles longer and reduced bleeding, but you won't find many women on MN who believe it makes any difference!
I know this doesn't really answer your question, sorry! I know women for whom those meds really worked, and others who felt it made no difference.
If you haven't already, it might be worth researching causes & hormones to see if there's anything you can do.