What Causes Delayed Periods?

I am a software engineer working at Accenture. I am 22 years old and engaged. It so happened that just two weeks before me and my fiancée indulged in a sexual intercourse. Though he entered me he made it sure that he ejaculated on the bed and it did not touch my vagina.I am not sure if a girl can conceive by sleeping on the bed he ejaculated even though it did not touch my sensitive part. My periods usually fall on 4th or 5th of every month. Since we both were virgins, and since i have not got my periods yet i am really very scared. He is currently in Dubai and our marriage is in December. I was just going through the net for some initial symptoms of pregnancy and even though i am not facing any of those i am really worried. I would like to meet you in person regarding this. Please elaborate on this regard.We know that we did a huge mistake by indulging in intercourse before marriage.Please ease my mind madam, you are the first person that came to my mind during my anxiety. Hope you understand my anxiety as i have refrained myself from sharing it with anyone else.