Pregnant?

So I had sex for the first time on March 4th. I've been on the pill since October and have been taking it every day at the right time. I also got off my period that morning. I'm worried though because I've been getting really bad stomach aches and back pain. I may just be paranoid but I am nervous. I'm only 18 and still in high school. I dont want a child yet. Please dont be negative in the comments, just tell me if I am or not. I might just be paranoid and my bf isnt helping that very much XD