Thanks ladies, feeling so relieved reading these experiences about effects on menstrual cycle due to a Cortisone shot as I couldn't find anything online. I got the shot on my right shoulder for calcific tendonitis on 17th May, got relieved with the shoulder pain thankfully, was due for my menses by 21st May which got delayed by 7 days (have been regular all my life with rarely +/- 1 day). Thought i was pregnant but the test was -ve and now i started spotting since yesterday with extreme cramping like back in teens. My physiotherapist seems to be relating the back pain to my cervical disk bulge. Will be visiting a Gyn to check if theres any other mess happening in my body