Fertilization of the fertilized egg usually occurs about 6-8 days after sex, and it takes about 12 days for the fertilized egg to fully implant. After fertilization, frequent urination may occur, as well as vaginal cramps with a small amount of vaginal bleeding. Some women also experience pregnancy reactions such as picking up food, breast swelling and pain, and darkening of nipples and areolas with Montserrat nodules. After the fertilized egg is laid, the syncytial trophoblast cells begin to secrete chorionic gonadotropin, and a blood test can detect whether or not you are pregnant, which is the earliest way to know if you are pregnant. If you do not have your period for more than three days, you can also use a morning pregnancy test to detect pregnancy.