How long does it take for Armour thyroid to work?

I've been taking armour thyroid for 3 months. I started at 30mg, then 60, and now 90mg and have had no change. I have had severe, constant fatigue, joint pain, and heart palpitations for the past 10 months. None of the doctors I've been to know whats going on. All the test I've done have come back inconclusive. The only reason I'm take Armour is because my sister (and deceased grandmother) has hypothyroidism. Does anybody have a clue or a suggestion or something. I'm running out of hope.