What Causes Weight Gain Along With Pain In Joints While On Armour?

I had been on Amour thyroid for about to years but I started noticing it was not working. I was switched to Synthriod and Cytomel but felt terrible, bloating while taking it. I when back on Armour and then switched to Amrour NP. Since the changes I have done nothing but gain weight, tired all the time, and joint pain. I am tempted to go off everything.