As neonalee mentioned, if there's anything good to be said about thyroid cancer, it's that it is slow-moving. But first things first: an enlarged, heterogeneous thyroid is not necessary cancerous. Thyroiditis, or inflammation of the thyroid, is not uncommon in hypothyroid/Hashi's patients, including myself. This can lead to swelling, which is sometimes relieved once taking proper doses of thyroid medicine. (Are you currently on any thyroid meds? You did not say, but it sounds like since your hypo symptoms are flaring, it is time to up your dose.) Thyroid nodules are also not uncommon, even in people with normal functioning thyroids. In my case, US reports noted "hypoechotic lesions" which were probably prominent lymph nodes. In the case that the nodule is suspicious, the next step would be for the doctor to order a biopsy using a fine needle to test for malignancy. Again, I would not worry too much until you can consult with a doctor. You will drive yourself crazy with anxiety if you try to diagnose yourself solely through internet research!
If you are anxious to see your doctor sooner, try calling the doctor's office back and explain that your appointment isn't for another two months, but you have questions about your US results and that you are anxious to get in sooner if anything opens up. If you ask nicely, they may keep you in mind in case anyone cancels their appointment.
I don't know what any of those medical terms are, and I can't tell you what to do. BUT, if I were you, I would do some research on iodine & Dr. Brownstein (who says iodine is ok for Hashi's). I also have a HUGE goiter and both my Endo & my ENT say that if I had to have cancer (I don't), thyroid cancer is the best one to have because it grows so slowly and is easy to remove.
I have no answers for you, but I hope this helps at least a little while yo uwait.