I have subclinical hypothyroid with tsh 8.10 dr. gave thyroxine 50mcg then tsh .10 dr. gave 25mcg but my tsh more down with hi heart beat what is this?

Subacute thyroiditis: It sounds like you have gone from being mildly hypothyroid to hyperthyroid. This can happen when there is superimposed inflammation of the thyroid (subacute thyroiditis). This can be seen in autoimmune thyroiditis. In your age group it is most likely either graves disease or "hashitoxicosis". You should see an endocrinologist to help figure it out.