I don't know what to do , I need help

okay the last time I got my period was April , I still haven't gotten it ! I don't know what to do , I took two ept pregnancy test about a week ago both came out negative . I have on and off cramps for the past 3 days it feels like I'm going to get it then it goes away & tomorrow I have an appt to get on birth control w my mom . can someone help me