Hello
I have gone through your question.
I can understand your concern.
Hashimoto's tiroiditis is the most common cause of
hypothyroidism.
Weakness and weight gain are symtoms of hypothyroidism.
This symptoms disappear gradually after starting the thyroid
hormone replacement therapy.
I suggest to consult an
endocrinologist in your area because you need to start
levothyroxine or
thyroid hormone replacement therapy.
6 weeks after starting levothyroxine,it is necessary to repeat the TSH test and than adjust the dosis accordingly.
After e couple of weeks with this therapy your thyroid tests will become normal ,your symptoms of hypothyroidism will disappear and your metabolism will return normal.
In this circumstances,it will be more possible for you to loose weight,especialy if you do more physical activities and start an hypocaloric diet.
Hope i have answered to your question.
If you have other doubts,feel free and ask.
Regards.