Pre rsd and pn dx I had a fever for 2 plus years every other month. I would be sick with a fever then it would go away and a month later come back. This was a cycle non stop for I would say more then a few years. I went to the doctor multiple times and the why behind that never was found. Odd thing though when I developed rsd 4 plus years ago I have only been sick with the flu one time. Now I have other major problems from ears,eyes,skin,I could go on plus the limb pains. I also pre all this had high liver enzymes and pancreatitis issues. I try to be careful now with over the counter meds etc.
I know one pain doctor I saw said that peope with rsd are more prone to infections etc.
Have you been to a rheumatologist? I would if not.
Hang in there and feel better