PrincessBear, there's a lot of misunderstanding about taking thyroid hormone replacement. If you need it for any reason, you are going to need it for life. If you take it when you Don't need it, it is going to make you ill, and you have to come off it. You Don't have to stay on it just because you've started taking it. That idea is crazy.
The fact of taking it doesn't mean you have to stay on it for life, you have to stay on it for life because you need it and will die without it. It's as simple as that. If your gland can no-longer make the hormone you need to live - for whatever reason - you have to take it. I know I'm repeating myself, but I can't stress this enough.
You obviously need it because you have antibodies that have quite obviously damaged your gland. That's what they do. And that causes symptoms. Weight-gain is one of them.
Soy is doubly bad for people with thyroid problems because a) it stops the thyroid gland from absorbing the iodine it needs to make thyroid hormone; and b) it stops the thyroid hormone that is made from entering the cells. You already have problems making enough thyroid hormone due to antibody damage, consuming soy will make it much worse. It is not a health food, and isn't really good for anybody unless it's fermented. We've all been conned with soy!
Going to the gym won't help, either, because exercise uses up the all-important thyroid hormone, T3, which you are going to be short of because you have a damaged gland and you are consuming soy. So, no Wonder you feel as if you're killing yourself!
Thyroid hormone replacement is not 'medication' in the normal sense of the word. It isn't a drug. It is live-giving hormones. Taking it does not make you a whimp, and it does not make you a junkie. It keeps you alive.