I don't know if I'm an expert, but I have had thyroid cancer, had my thyroid removed, and now deal with medication issues. At the time my thyroid gland was removed, I also had Hashimoto's thyroiditis but I was asymptomatic and didn't know it until the gland was removed. When you mention antibodies, I assume that these antibodies indicate that you have this condition?
As for weight problems with thyroid...that is a tough one. I have spent weeks were my TSH is around 100-150 which is EXTREMELY hypothyroid. During that time, I have only ever put on about 6 lbs.
I have read several reports that hypothyroidism or thyroid "troubles" can really only account for a 10 lb weight gain. Most overweight people who are treated with thyroid meds only drop about 10 lbs if they do nothing else at all.
So, I think I would agree with Chimera that you should probably first look at what you are eating. I know you think you are doing well or all the right things (I know I thought I was), but often times we aren't. Journaling your food into
www.fitday.com is the perfect way to see what your caloric intake is. I thought I was eating right but when I logged it in I was at about 2,300 calories. And that was after I started my "diet". I've since fixed it and am now at about 1600 calories and the weight is coming off. It may not be enough to just get your carb to protein ratios right. Calories still count.
I think if you really track your food and are honest about it and can still prove that you are intaking few calories, you can then probably get an M.D. to give you some thyroid meds. They don't just like to arbitrarily treat the thyroid because excessive thyroid hormone causes its own problems. Also, according to my endo, most people who have too much thyroid hormone have a ravenous appetite and end up gaining weight. I know when they've increased my dosage of meds, I thought I was going nuts and was eating everything in sight.
Additionally, my best friend was kind of in the same boat as you. She is 5'8" and weighed about 180 lbs. She would exercise every day and thought she was eating well. Couldn't shed a pound. She found a new GYN that believed that thyroid troubles ailed the world. She tested my friend and her TSH came back as a 2.0--which is really ideal. She put my friend on thyroid meds. She did not lose weight, but she was very cranky.
Edited to add: My friend stopped the meds because we all told her how mean she was. She then started weight watchers and went on to lose 35 lbs which she has maintained for a year.