Weighting,
Your history sounds truly frustrating, but I can relate to the ups and downs of it.
You need to get your T3 tested in order to gauge your T3 levels. TSH does not test your thyroid at all, but tests your pituitary gland to see how much of the stimulating hormone it needs to release to stimulate your thyroid gland. The more it releases, the slower your thyroid is. This is a good test for someone with a really slow thyroid, but the TSH test cannot tell someone whether their T3 or T4 levels are off balanced.
I'm not a doctor, but from 4 years of research and a good relationship with my own doctor, I know that you need to get T3, Free T3, and Reverse T3 tests performed to get a good estimate as to the level of usable T3 in your system. You really want to get your T3 tested specifically, because T3 is the hormone produced by the thyroid gland that regulates energy & metabolism.
If you get a T3 test, it will tell you specifically your T3 levels. If you get Free T3 tested, it can tell you how much of your T3 levels are available for absorption into your body. You should get both tests done. You could also get Reverse T3, to see how much your body is attacking the T3.
If you are on Synthroid, you are only taking replacement T4 medication. Although the body naturally converts T4 into T3, it does not convert it when replaced by medication.
You can check out my own journal online at
http://diagnosis.4t.com if you are interested in any of this. I have some cites to support some of the thyroid information I posted in this message.
In the meantime, I suggest you check out Mary Shomon's site at
http://www.thyroid.about.com and go to her Top Doc Directory to find a recommended doctor in your area.
My e-mail is on my site - feel free to drop me a line if you want. And good luck!
Margie