I know it's difficult to find a competent endocrinologist, but I would strongly suggest you keep trying. An enlarged thyroid and sudden weight gain are worrisome.
What imaging have you had? Have you done tests for Lyme disease? (Westernblot, Elisa, PCR) Did you get tested for Grave's disease? For Lupus, there is no single test that can accurately diagnose you, but there are typical symptoms and your doctor would typically diagnose it by writing down these symptoms and running tests to rule out other things.
The first goal imo is to find out if the thyroid is the cause or a symptom and go from there in excluding illnesses. Wish you well on your journey