I have been having a lot of trouble with rapid heart beat. I was...

I have been having a lot of trouble with rapid heart beat. I was taking 112mcg. which my endocrinologist increased to 125 because of my blood results, and then the heart problems kicked in. Since then I have tried all sorts of dosages, even going off it for a couple of days (which did calm my heart down considerably). I'm working with 75 mcg now, but after 7 days of that, my heart start pounding away again. I had thyroid cancer so I have to take some kind of hormone replacement, but this is a challenge. I am wondering if Armour might work better.