Francesca-
I'm sorry, it sounds like you've had a terrible time. I'm not completely clear on what you have already done or the reason you have the Mirena, so I'm going to assume it is due to heavy bleeding. Have you considered a procedure such as an endometrial ablation? Basically, this procedure (there are several names for it, related to the device the doctor uses) blasts out the lining of your uterus.
By the time you are peri-menopausal it is not uncommon to have a super thick lining in your uterus and abnormal bleeding. I personally had this problem for several years and became quite anemic. Two years ago I had an endometrial ablation, and it worked famously for me. My doctor used a little laser device to sort of blast out the deep lining in my uterus. I did not have fibroids or anything. It was an outpatient procedure, the recovery was minimal, and since then I have had very light periods. My understanding is that after the ablation you might have no period, light periods, or eventually return to a normal flow, but it eliminates that crazy heavy bleeding.
If peri-menopausal menorrhagia is your only problem, I highly recommend looking into ablation as a possibility.