How long can hyperthyroid go (i'm already pretty anorexic looking from this now) before there is major or unreversable damage if any occurs?

Huperthyroid no Rx. If you have hyperthyroidism and have had no treatment then you are playing with fire and it is bad for you.Not only you will loose weight, but you may get tachcardia and other arrythmia in your heart.It is not a good idea not to get treated.Itcan be treated with drugs or radioactive iodine therapy.You should not fool around with this condition as you are already loosing weight.
Depends . Depends in how severe it is. Generally little permanent damage. Unless there is eye involvement. But that is highly variable and has little direct correlation with thyroid hormone levels themselves.