Since you always seem to get stuck at the same weight, it might be something I read about, where people tend to stay at a weight level where they have spent a lot of time previously.
My mother went down quickly to one level she had been at for years, then went down to her high school graduation weight, though that's still too much, and is losing again now after a long stall.
You might need to just hang in there and get past that barrier. Your body is expecting you to cave then...trick it by not doing so.
And definitely get that thyroid problem taken care of.