Suggest Treatment For Delayed Period,cramps And To Conceive

I have had multiple abnormal papsmears in the past. I am 20 years old. I have another schedule for the 14th. I am on birth control and have never missed a week. This past week I was supposed to have my period but it never came. I have been having crams recently, but it is impossible for me to be pregnant. What could be the cause of this?