Here's some encouragement, Miserymum.
I have had the mirena for 5 1/2 years now. The reason it is still there after 5 years is I have reached the menopause and I was told I could leave it for an extra wee while for contraception. I'll need to get it out soon.
I THINK IT IS THE BEST THING SINCE SLICED BREAD AND IT WAS A COMPLETE LIFESAVER FOR ME, SO PLEASE DON'T DISCOUNT IT!
Like you, I had really heavy periods with clots. I flooded during meetings, in people's houses etc. It was a miserable situation and I despaired.
The insertion was very painful, but the doctor had decided to give me a biopsy first, "just to be on the safe side". I bled for 6 weeks afterwards (but not heavily) which was a surprise.
However, after that I didn't have a period for a whole year and once they started again they were as regular as ever but totally insignificant.....wonderful. Also my PMT disappeared.
I didn't particularly gain weight, didn't get spots...I was just my usual self but easier to live with and delighted to have such light periods.
Give the Mirena a try. You might be equally pleased.