Having read your first question again, it does appear that you may have hypothyroidism. A blood test
should confirm whether that is the case. But there may be other causes.
If your doctor won't test you for hypothyroidism, it may be worth seeking a second opinion to confirm the condition one way or another.
Onions, seaweed, diary produce, eggs, and other fruit and veg contain iodine, which is needed for the thyroid gland to function properly.