I have been taking synthroid for 10 years and for 9 of those year...

I have been taking synthroid for 10 years and for 9 of those years everytime I get a dosage the doctor thinks will get my readings to a safe level, I begin to have heart palpitations to an extent that I pass out. At first I was rushed to hospital several times from passing out in public places. I also have leg cramps, coroited artery aches and the inevitable weight gains. Finally my doctor sent me to an Endro this week and he claims he has never heard of side effects and tells me to increase me dosage slowly. My readings are suppose to be between 4 and 5 and they are 26! He treated me like I was a hysteric and told me not to breath so hard when I am having palpitations. Someone mentions a balance between T3 and T4 can someone explain. I am so happy to know there are others like me out there. Sally