Any other medical problems or medications? Are you coughing any thing up? Do you smoke?
Hmm. That is very curious. I suspect that your symptoms are not related to the lobster- I think that this is (for lack of a better term) a 'red herring'.
It sounds like you have alot of rather vague symptoms which could point to systemic illness, like an autoimmune disease or a hormone deficiency (low thyroid). Lupus and rhuematoid arthritis are the most common inflammatory arthritides which are tested for, there is collagen vascular disease, sjorgens, etc.. Fibromyalgia is also a consideration. I noted that you recently changed thyroid medications- perhaps your body is absorbing the new medication differently and the dose needs to be adjusted.
In addition, certain malignancies, such as lymphoma and leukemia can give you vague symptoms of fevers, weight loss, night sweats, enlarged lymph nodes and even rashes As well, certain vitamins deficiencies can cause the same symptoms. Finally, an indolent infection such as HIV can give you the same symptoms. Other ones include tuberculosis. Not to mention other immune deficiency syndromes. So, I would:1. consider a consultation with a rheumatologist2. ask about vitamin deficiencies.3. get tested for hormonal abnormalities- recheck your thyroid4. consider a consultation with an infectious disease doctor and immunologist if the other steps above are negative for disease. The last thing this could be would be stress, but that is more of a diagnosis of exclusion. I would talk to your GP about the above possibilities before deciding that it is stress-related.