Levothyroxine Sodium and thyroid

For the last year and a half I have taken Levothyroxine Sodium 50mg, now increased to 75 mg. I have gained a great deal of weight and developed arthritis in both knees. Some days my knees hurt so bad I can hardly get out of bed. Since my medication was increased to 75mg. I have been itching like crazy. It is not continually, but at times I just go into an itching fit. Please help! Is there any other thyroid medication that works without all the bad side effects?

I have taken this Levothyroxine ever since I got Thyroid Cancer in 2006. And thank God I am free from cancer now. My main problem now is that, sometime I really don't know what was wrong with me and get confused over my own feeling. I do have cramps, sleep problem, headache, menstruation problem, mood swing, panic attack and always thinking of a negative thing eg like am I going to die. It has been bothering me since than. Please help I just wanna know is this really due to the medication or its really that I am going to die. I am very confused at times when feeling this side effect. =(