Does Contrast Used During CT Scan Cause Dark Colored Stools?

I had a CT Scan with contrast three days ago. Day after CT scan I had a uterus biopsy. The Next morning my bowel movement was half off cream color and half black. Now a day and half has passed and I have no bowel movement which is very unusual for me. Do I need to be concerned for the black color of my bowel movement? Is CT scan with contrast or biopsy had anything to do with it?