There are 5 types of thyroiditis. The two below might fit your discription. One of which robotom discribed.
Painful Thyroiditis - subacute granulomatous thyroiditis, De Quervain's Thyroiditis: Usually starts out as a harmless viral illness such as the flu or a cold which invades the the thyroid gland causing thyroiditis. This type of inflammation is quite painful the front of your throat is sore to the touch. Pain extends to the jaw or ear Sometimes only one lobe of the thyroid is affected causing pain and swelling on just one side of the neck instead of both.
Aspirin or ibuprofen can be taken to help decrease the amount of pain. If the thyroid cells recover, no additional medication is needed. However, if the damage is permanent, replacement doses of thyroid hormone medication must be taken for the rest of your life to treat the hypothyroidism.
Acute Suppurative Thyroiditis - rare caused by a bacterial infection in the thyroid which causes pus to collect and form an abscess within the thyroid gland. The bacterial infection may be carried in the bloodstream from anywhere in the body or it may come from the throat itself.
Antibiotics and surgery to drain the pus can result in complete cure.
GL
I am experiencing something very similar to what you are describing, except that the fatigue is not as bad in my case. It started as a persistent sore throat, possibly strep throat (I never had it diagnosed because it wasn't severe). After several weeks, the thyroid area of my neck became sore and felt enlarged, but only on the right-hand side. I was traveling at the time and didn't do anything about it. Gradually, I developed additional symptoms: Feeling hot and sweating a lot (especially at night), rapid heartbeat (mine is normally very slow), feeling weak and getting tired easily (especially at the end of the day). I attributed this to the stress of traveling, but the symptoms persisted after I came back home. I'm about 6 weeks into this episode now. The sore throat and flu-like symptoms are gone, but I still have the sore thyroid and the other symptoms.
I did some research on thyroid conditions and found that my symptoms match very well with subacute thyroiditis, also known as 'de Quervain's thyroiditis.' There are many excellent articles about it on the web, e.g.
http://www.emedicine.com/med/topic2276.htm
In short, this condition is typically caused by a throat infection, with the inflammation spreading to the thyroid. Hyperthyroidism symptoms develop and can last for weeks or months after the infection is cleared. I think the pertinent information for you is that the thyroid hormone levels can fluctuate, and are typically high in the early phase, and become lower than normal in the late phase. Therefore, your hormone levels don't necessarily look abnormal at the time you take the test; you might have to take the test several times or at different times of the day.
The good news is that the condition is self-limiting in almost all cases. The symptoms can be relieved by anti-inflammatory therapy. I'm taking ibuprofen and naproxen (alternating), and this seems to help a lot.
I hope this helps somewhat. I would be interested to see some comments from medical experts. It seems to me that your doctors don't know the literature very well; otherwise they would know that the thyroid test may come out high, low, or normal at different times. It seems to me that the only conclusive test would be a thyroid biopsy ("Thyroid biopsies in subacute painful or granulomatous thyroiditis show characteristic multinucleated giant cell granulomas and a mononuclear infiltration").
As for myself, I'm going to wait to see if this goes away by itself, as long as the symptoms don't get worse. I can function quite well, as long as I take the anti-inflammatories.