severe problems with thyroid

can anyone help me I have been on thyroxine for years now and was always on 100 mg then the thyroid changed and they upped my thyroxine to 125 mg then my weight went up and up and up I was 9and half stone I am now eleven stone I have other medical problems on top and am really worried as I cannot carry this weight i have myasthenia gravis and bronchial asthma as well as thyroid and am finding it very hard to function, I keep swelling up in my hands fingers and feet, my legs have given way twice, and i feel so tired and fatigued, been the docs so many times and I was told it was down to my age but this happened about 4 years ago so its not my age I am at my wits end and its making me feel very down can anyone out there give me any advice you can get me on my email its jen7pur@aol.com. Thanks x