Sweetie don't stress ok! Periods are not always gonna be totally regular....we are not machines, we are human beings. Try not to think about it for a little while and if your period still does not start for week or two then take another test. And, know that in the end all things will work out. I got pregnant by surprise this past year and I was sooooo freaked out and upset. But, now I realize it was the best thing to ever happen to me...the baby I thought I didn't want is now the most beautiful little person I have ever seen. He smiles at me so big and my heart melts. I know how you feel right now sweetie.....please try not to worry ok!!!