Pregnancy is a possibility. Flomaster95 gave the best advice. Don't stress it or worry about it so much until next month. If you don't start take a test. The reason not stressing it or worrying about it is important is sometimes our bodies will start having symptoms of pregnancy. I had syptoms for three months really thought I was pregnant and then started out of no where.
I'm no doctor by all means, but its still possible you could get pregnant. Some people get pregnant while on their periods (sexual intercourse during your period) so I'd wait till next month before you start worrying. If you haven't started, take a pregnancy test.