I have psoriatic arthritis. You could have an autoimmune issue with it, or your body is just struggling right now with the adjustment. It is common to get feverish during a flare. I have immune issues. I've been told the PA has affected not only the joints, but the lining around the joints = which is what is actually inflammed at times and not the actual joint itself. This has also affected (I'm told) my organs. It seems to move and hit an area hard for a while, I work to get past it, level out, then it finds another weak spot.
I take a super b complex that helps with fatigue. last year, i was sick a LOT...we're talking every 2-3 weeks I was in bed for a few days with fatigue and fevers. I found out I was vitamin D deficient (down to a 13 - normal is around 32, they say.) I've been taking vitamin D supplements and my level has been slowly rising. I have not been sick nearly as much this year. Possibly a coincidence? I don't know.
Psoriatic arthritis supposedly shows up different on xrays because it affects the joints differently than RA. However, when I was diagnosed, the pain and the problems were there, but (thankfully) the wear and tear on my joints at the time was minimal. But, I had a bunch of other symptoms that made it clear to the doctor at the time what my dx was.