What Causes Hand And Feet Pain With Morning Stiffness While Breastfeeding After Low Iron From A C-section?

I have a hand and feet pain . Stiffness in the morning and then gets better but still I have pain. My doctor order RHomotology factor test and sedrate and c protein test . R factor is negative but I have a sedrate of 40 and c protein 0.5 . I am breast feeding and I had a low iron level due to blood loss during c section. But my iron leve is better now but still not normal