I was on the birth control shot for a few months. I missed my last appointment to get another a month or so ago. Here in the past month I have had really bad cramping almost like someone is stabbing me in my unterus or something. My nipples are very tender. Could I be getting ready for a period or could it be something else? My mom had cervical cancer twice and I am worried that it could happen to me. My great grandmother had it as well. Is there anything I shouldbe worried about?