Abdominal cramps and back pain after period

Diana
My period just ended 8 days ago and now I have crazy back pain and pain in my pelvic area. The back pain is horrible at night and sometimes during the day usually if I walk I'm fine or if I'm standing if I sit it'll go away. The pelvic pain is constantly coming and going no matter what. It's not unbearable but it's not normal and I'm getting worried. I don't think I'm pregnant I took a test and plus I went to the emergency room they didn't help AT ALL. Has anyone ever experienced something like this? I'm starting to think I'm crazy