Armour Thyroid and tsh

My doctor prescribed Armour Thyroid to me to help me lose weight; he did this without taking a blood test. My thyroid was perfectly fine when I began taking it. I took it for three weeks, but didn't like the palpitations and weird things happening to my heart so I stopped. Since then, about two weeks ago, I have had horrible muscle cramps in my upper back, neck and shoulders. I also have pain in my right arm which I am assuming is a pinched nerve from the muscles. Any ideas what to do?? I can't take the pain much longer.