I don't know if you like swimming but I know that it is really good for the low impact side of things. It doesn't even have to be lap swimming, water aerobics classes can really kick your ass! It is amazing that you can actually sweat in water. I was going to mention the eating enough calories thing too but someone beat me to it.

I think the most frustrating thing about dieting is that the results aren't immediate. But the only other thing that I would say (as I know hypothyroidism is a problem with some of my friends and relatives) that if you're still not seeing results in a few more weeks it may very well have to do with stress, post-menopause or something else health related.

Keep it up I am sure you will reach your goal!