If you are pregnant you may or may not experience the changes described here. They may happen earlier or later than they appear on this list, and some may continue throughout the pregnancy. Pregnancy is counted from the first day of a woman's last period. Your period stops or becomes very light. You may feel nausea or queasiness.
Some women vomit.
Your breasts swell and may be tender. You have to urinate more often. You feel tired. You may have headaches. By twenty-one days after fertilization, the embryo's tiny heart has begun beating.