I was wondering how late should a period be before being concerned about pregnancy. I have never had sex, but it is possible that pre-ejaculation and possibly some semen got near the vagina. I dont know if it got in, but a little in the area. I suppossed to get my period a day or two ago and I am usually on time. Is it possible that I am pregnant? Are there other reasons to explain late period? How late should my period be before I start being concerned?