You have Hashimoto's and are you are hypothyroid. The pain in your thyroid is oxidation (burning) due to both selenium and Iodine deficiency.
Cannabis suppresses thyroid hormone and you don't have much to begin with.
I would start all companion nutrients and do salt loading for a month before starting iodine. And read Dr. Brownstein's book and seek out an Iodine literate doctor (companion nutrient protocol and doctor list at Breast Cancer Choices website).