Goodness girly... I don't know if you are pregnant or not but like smjmekg said relax and try to take it easy =) I know that this is probably obvious for all of us, but I recommend you see a doc and get yourself on some birth control (pills, shot, nuvaring, something) to avoid an unwanted pregnancy. I hope that you feel better and please, please, please protect yourself!
You can get pregnant the first time you have sex, you can ANYTIME you have sex, especially if it's unprotected. The best thing you can do is to stay calm, don't stress too much and when your period is due use a home pregnancy test.