I am on day 13 of my missed period and I know for sure that I am not pregnant. My last cycle was supposed to be on nov 27 to dec 1, but I missed it and im almost two weeks late. It is very confusing because I have been getting cramps in my lower abdomen for over two weeks so I start to think that I will get my period soon. I check every time after I urinate but nothing. I did some research and found many causes of missed periods but not pregnant. I keep getting cramps under my belly button and I think that is a sign of an ovarian tumor or ovarian cancer. I don't know if I have it, but I just want to be safe. What should I do?