Allergic reaction to iron infusion

Has anyone experience and difficulties while getting infusion done , I almost completed my 1st session before I ended up in excruciating pain in my back ( sharp shooting pain) it was hurt more if I moved or breathe, they stopped it immediately and gave me different types of medication to calm it down, I’m currently still in a little pain ( at home) but they said if it doesn’t get any better to call my ob , I have to go back next week I am terrified because I was in a lot of pain I don’t want it to happen again .