Clutching at straws here. Since having 4 year old ds, I have suffered from prolonged, very heavy periods which occur every two weeks. I would bleed for 8 days, would get a break for 7 days, then start again.
Have tried the mini pill, which made me bleed continuously (although not quite as heavily), and am coming to the end of a trial of the Depo injection. I loved the Depo before I had ds, it eradicated my periods completely, but now it just makes me bleed continuously(last one was 17 days) and for at least 50% of the time.
I had a scan, in case it was a reoccurence of a dermoid ovarian cyst I had years ago, but the scan was fine.
I have asked to be referred to a gynaecologist, but my GP insists they would just try the Mirena first, and that I should try it before she refers me. In answer to my question - why am I bleeding so frequently/heavily since ds, she says 'some women just do.' 
She is convinced the Mirena will sort it, I am less convinced but will have it fitted later this week. Am not looking forward to weight gain, as I still struggle with a spare stone of baby weight as it is.
So, has it worked on this kind of problem for anyone, and is my GP right, that some women just do bleed more frequently and heavily?