It is possible to feel deathly ill with a more lower TSH. Or in your case, hardly feel anything. Don’t rely on the TSH test. Ft3 and Ft4 are better indicators of Thyroid health.
Get your Ft3 and FT4 levels tested. Your meds should be adjusted on the basis of these, not TSH. FT3 and FT4 should generally be mid to upper 1/3 of the range, depending on where you feel best.
Particularly in people with long term hypothyroid TSH tends to become less accurate.
TSH is often an unreliable indicator of thyroid status because it can be affected by many factors other than thyroid hormone levels.
With a TSH of 700, I would expect you to be barely functioning if TSH were acurately reflecting free T3 and free T4 values.
TSH, in and of itself, causes no damage to your body no matter how high it gets. However, you should repeat TSH and make sure FT3 and FT4 are ordered as well. If FT3 and FT4 support your TSH (i.e. they are very low), then you would want to increase meds (I'm assuming you're on meds) or change meds.
Considering your symptoms (or relative lack thereoif), I would guess that either the lab made an error or you have a pituitary issue going on.
When was you last labwork before this, and how did things look then?