Thanks for the additional information. Well, 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). I am particularly concerned about the night sweats. Lupus and rhuematoid arthritis are the most common inflammatory arthritides which are tested for, there is collagen vascular disease, sjorgens, etc..
That being said, another possibility that is frequently overlooked is heavy metal poisoning. many metals can cause vague (but very real) symptoms of fatigue, unusual rashes, joint pains, etc... you might be in contact with these and not even know it.
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 heavy metal poisoning3. ask about vitamin deficiencies.4. get tested for hormonal abnormalities5. consider a consultation with an infectious disease doctor and immunologist if the other steps above are negative for disease.
This should get you started!