I started to experience the same kind of periods that you are describing back in Sept. Oct. 2006. This continued thru the first of 2007. I started out taking kelp and this took my periods down from 2-3 weeks of heavy bleeding with lots! of huge clots to 4-5 days of heavy bleeding with lots of large clots.
I then started on Iodine - Lugol's detoxified and Iodoral at different times and my last two periods have been like the periods that I had in my 20's. With the exception of a little more cramping. I am mid-40 ish.
If you research iodine, you will find that it really effects all of our reproductive organs.