What Causes Delays In Menstruation?

i am 51 years old and happily married with 5 children. Last month I received a cortisone shot in my shoulder, to releave pain that I had for the past 6 months. My period is late and i am having cramping on and off for the past week without any bleeding. I have always been regular and the only time i was late was with my 5 pregnancies. AFter looking on the internet - i've read that some woman have a problem with their mentrual cycle shortly after having this shot. What is your opinoin?