My problem

Hi. Ok, so I have a problem. I had sex with my boyfriend a few times this month. The first time was when it was my second to last day of my period. He pulled out. Two days after I finished my period we had sex again and he pulled out. The next week we had sex but with condoms. My period usually comes around the 30 or 31 of every month. I still haven't gotten mine. I also spotted on the 21, 22, and 24  which I thought was weird it skipped a day. Unless it was a light period because I also thought it was strange it used more then other said if I was spotting. I tested 2 weeks after we had sex and it came back negative. I am going to test again this week, but I was just wondering what is wrong if I didn't get my period? What do I tell my family if I am pregnant, it will never fly. 
We are just in college. Please help me.