Back pain

Received 2d infusion of Opdivo today for stage 4 subcutaneous melanoma. After first infusion 28 days ago, no side effects except for exhaustion. Today, all blood work was good but a strange thing occurred 7 minutes into the treatment. I experienced excruciating low back pain. The extra sharp pain was constant and continued until a sedative and steroid were injected through my IV. After waiting about 30 minutes, the infusion
Continued, but at a slower rate. I can’t fully explain the severity of this pain. One nurse said she had been in the lab 11 years and never witnessed this. She later said it happens in 50% of infusions and later said 90@ of them. She didn’t know what to do and called for assistance. Four other nurses responded and seemed to understand what to do. I did completer the infusion. Next month (28 days) they will give me a prior dose of Benadryl and infuse at a slower rate. I am home now and feel well except for the always present exhaustion. One last note, the supervising nurse told my nurse that this was the second batch of Opdivo this afternoon that caused a severe reaction soon after the medicine was infused. Has anyone experienced this back pain during infusion?