Implantation is the process of the fertilized egg attaching itself to the inner lining of the uterus. At the end of four days of multiplication of the nucleus, the morula is covered by a sac like structure called the blastocyst. The cells around the outer surface of the blastocyst continue to divide till the end of seven days to form multiple finger like projections called chorionic villi. By this time, the embryo reaches the uterus and the chorionic villi burrow into the upper layer of the lining of the uterus. The villi open into the maternal blood vessels in the uterus providing the egg with necessary oxygen and nutrients.
Implantation normally takes place in the upper and back part of the uterus. At this stage the blastocyst is not visible to the naked eye. Since you have NOT missed your first menstrual period, you will not know that you are pregnant because other symptoms of pregnancy also do not start until several days after implantation.