I am much in the same boat, I had cancer and a TT in June '09, RAI in July '09, but now, May '10 I finally feel well. BUT! I was also on .175 levothyroxin, I begged the doc to up my dose, because I just didn't feel like my old self...I couln't get through the day without lots of caffeine, and my body felt heavy, I was not loosing the weight I gained. He told me that it wouldn't really help, but to take 1/2 of a .025 pill, which upped my dose to .1875...well, that made a huge difference. Keep trying to find the right dose. Don't give up. As cancer patients, our TSH should be less than .01, we have no thyroid to stimulate, so if our levels are correct, we won't produce any TSH. Check your records (I always have my doc print all test results for me and keep it in a file), and see where your TSH is. Good luck.
Radiation or thyroid cancer RAI is very tough and effects the entire body regardless. Overall - in addition to Goolarra - conversion issues of using T4 medication only will never stabilize you and the T3 hormone ( only tested on labs by a specific FREE T3 test) will determine if you have enough direct T3 hormone flowing to give you better health.
I agree - for 6 years you are in a muck of treatment and probably being sweeped under the rug in proper treatment.
Ask your doctor for the results of all tests that he has run. A printed copy is best since you can keep this in your records and it will include your lab's reference ranges. He has to give you these if you ask for them. Once you have those, you can post them here if you'd like, (with their ranges) and members can help you interpret them and make suggestions on where you should go next. Six years is way too long to take to stabilize your levels. My guess is that your doctor is not doing adequate testing and/or doesn't know how to interpret results.