What Causes Swollen Lymph Nodes In Arm Along With Fatigue And Joint Pains?

I have swollen lymph nodes in my arm (elbow area). I haven t been feeling well for 3 months (severe constipation, fatigue, joint pain, feeling full sometimes after small meal, swelling in legs/feet on occasion). I had a colonoscopy so all good there. I do have RA but the pain is worse than anything I ve ever felt. Now the lymph node enlarged. I never knew there were lymph nodes in arm. I m going to get CBC blood work. What could this be a sign of.