Tamoxifen side effects

I started on (Sandoz) Tamoxifen 20mg a year ago and I was OK initially and then the side effects kicked in.  I also suffer from fibromyalgia and osteoarthritis in my small joints (hands, feet) and I ended up in agony all over my body.  I had shocking muscle cramps in my calf and thigh muscles at least twice a week - they are so very painful and difficult to 'counter stretch' in the middle of the night.  I then had a 6 week break and started taking 10 mg and although life was a bit better, I still could barely function.  With my specialist's blessing, I am now taking 5 mg/day and I am only just managing to have a reasonable life.  The cramps still happen now and again, my joints and muscles hurt, but a bit less and I will try to stay on this dose for as long as possible.  Even with this low dose I am getting hot flushes and especially in hot weather or when I get agitated.  I am desperately hoping that this low dose will still have some effect re. lessening my risk of a breast cancer recurrence.