It is strange that you did not have intercourse for one year and that too out of ignorance! Anyway, every novice couple may have problem with proper insertion. Do not get impatient; it is a matter of practice and gaining experience after each act.
Hypothyroidism usually causes weight gain. You may find enormous advises on how to lose weight. I will tell you three simple things. Proper control of thyroid function. Stop sugar in all forms (body will start utilising fat). Start exercising; at least 40 min/day (gradually reach to 40 min target). Anything more than these will add to your benefits.
You may conceive with this weight and hypothyroidism is not going to bother much under medical supervision.