What Causes Joint/bones Pain And Fatigue While Having Low Hemoglobin Level?

my hemoglobin level is at 6.4, i am taking iron supplements (dr prescription). in addition to extreme fatigue, my bones and joints: knees, ankles, hips, and so on... have started to ache really badly. i'm 47 yrs old and am exhausted from all this medical problems. i haven't even listed them all. thank you for any suggestions or help you can provide.