Hi you can have RA without obvious swelling But if this were so you would Still have Raised ESR as there will be inflamation in your body seems really unlikly to be RA with No ESR & No RF, I Know some people will jump on me to remind me of Sero Negitive RA But these would have raised ESR or Swelling showing Very rare None of Everything
you could get a Whole Body Bone Scan they inject you with a "glow in Dark" and scan you it shows any inflamation or Hot Spots in Body
i have RA & Fibro and Both these can make you feel Lousy so Fibro might be a good guess But if in Doubt if you can try to get the Whole Body Bone Scan