It’s possible that your reaction is to the formulation rather than the iron itself. It might be worth trying a different infusion (e.g. Feraheme vs. Injectafer). It might also help to take (or get infused) Benadryl prior to the infusion, if this is thought to possibly be an allergic reaction. To minimize your iron needs *any* source of bleeding should be controlled. If you’re female and menstruating then you might (for example) consider birth control pills to reduce menstrual blood loss. Has your stool been checked for occult blood?
Your iron loss seems too quick to merely be an absorption problem. We honestly don’t normally lose much iron unless we are bleeding or something is destroying red blood cells. Have you seen a hematologist? A surgeon wouldn’t usually be well-versed in all of the ways anemia can develop.