There is a myth that a woman is pregnant when she vomits early in the morning. But usually the vomiting and morning sickness starts after two months of pregnancy. The very first symptom can be the irregularity of normal menstrual periods. Those women having normal periods can identify pregnancy than that of others with irregular periods.
If the normal period does not start on the due date then you can confirm the pregnancy with in 8-10 days of the due period date by doing the H.C.G test. Even though you have confirmed pregnancy yourself, it is better to consult a gynecologist without any delay and make sure that the expecting mother and baby are in health.