So I had sex on October 13 and the condom came off while doing it two days later I bought contraceptive Plan B to make sure that I would not become pregnant. I got my period about a week and a half later on the acting date of October 25 and then my period lasted the normal amount of time. but then I was absent all through the month of November and I was supposed to get my period on the 28th of November. but now I am 16 days late I took two pregnancy tests and they both came out negative. is there a chance I could still be pregnant? Or is there a chance that I need to go to A doctor because I have been having really bad cramps for the past two weeks?