hand shakiness/tremors

I've been on 50mg of Synthroid for the past year, and over the past several months I have started to notice a slight shakiness / tremors in my hands. I take my synthroid in the morning, and there is usually no tremors in the morning, but then throughout the day, depending on amount of use of my arms, I notice a slight tremors when I hold something in my hands. I've been to the doctors office numerous of times to seek additional testing, and all my levels continue to appear fine. Is it possible, that if I switch from Synthroid to a generic brand, that this will go away. I've been interested in trying Amour, to see if this shakiness will be resolved. To complicate things, I am pregnant, so I'm unsure of changing my medication during the pregnancy, but I would love to get this muscle fatigue / hand tremors to disappear.