I'm on Thyroxine too, and frankly I find it makes little difference to me, except that my nails are less prone to breaking. I think I'm on the same dose as you, but I understand that it can cause problems if you take too much thyroxine too. I was actually pleased when my thyroid problem was diagnosed and expected to lose weight, as a friend of mine did, but it doesn't happen, which I find quite distressing. Ask your doctor to explain what thyroxine does and you should understand it a bit better.

After a year of dieting with the assistance of the doctor and a dietician, and even prescribed diet pills, I lost 5lb. Believe me, I'm much more overweight than you.

Did you know that if you don't eat enough your metabolism slows down, so even it you eat very little you can still put on weight as your body thinks it's starving and slows down. Eat regular healthy meals and exercise (if you aren't too exhausted). I'm told green tea helps boost the metabolism too, but it didn't help me. Maybe it'll help you.