Do you know if your anemia is a lack of B12, folic acid or iron?
Usually if one is low in B12, then extra folic acid is given, too. A lack of B12 can cause a lot of different neurological problems.
ampky is right, there are many reasons for anemia which is something to get evaluated separately from your fatigue and stiffness.
Other than testing for pernicious anemia (lack of intrinsic factor), other testing may include B12, folate, transferrin saturation, ferritin, and if everything else is negative, a bone marrow biopsy.
Some autoimmune problems can be ANA negative