Well if you were me, you'd be in for a whole lot of reading and research into this disease. Your symptoms sound like hypo and the fact that you're D deficient is a sign of it too. If you want to get your labs you can post them here and we can comment on them or suggest other helpful testing.
I suggest you read a lot of posts on this forum * Disallowed website and related information removed by hb-mod, moderator *
You can either go with synthetic (like he has prescribed) or natural thyroid hormones. They both have their followers and detractors but you need to know your treatment options in order to make an informed decision. Like you have found, this is a "for life" thing that there presently is no cure for. It does require that we are on top of it and I personally think that those who actively participate in their own monitoring and treatment do the best.
So welcome to the club
. You are not alone, as you will soon see if you hang around here!