Although commonly known as 'morning sickness' it is not limited to the mornings and maybe experienced at any time of day. It ranges from a light fainting sensation to nausea and violent vomiting. It normally occurs around the fifth or sixth week of the pregnancy but may occur as early as week two and has normally ceased by the end of the first trimester.
This is perhaps the most obvious and common sign of being pregnant but is not necessarily a true indication. A missed period may be caused by a number of different factors; stress, sudden changes in weight (especially weight loss) the after effects of being on the contraceptive pill, and other specific illnesses. If you are experiencing skipped or missing periods without explanation then you should check with your doctor.
This is another very common symptom and possibly one of the first that many women experience. It can be experienced from extremely early on in the pregnancy. The symptoms are extreme tenderness and enlargement of the breast and also the areola will become much darker in color. This is the breast preparing itself for pregnancy and breastfeeding. This symptom usually subsides after a few weeks.
It is quite normal to have moments of extreme tiredness during the course of the pregnancy, although it is normal if it becomes persistent or start to become uncomfortable then you should consult your doctor.
URINATION & CONSTIPATION:
As soon as you become pregnant your body starts to undergo a multitude of physical and hormonal changes. The womb is preparing and the uterus rises up towards the abdomen. This puts a pressure on the bladder and can lead to frequent urination and sometimes spontaneous urination. It may also cause constipation. These are quite normal and typical symptoms of being pregnant. The changing hormones in your body also affect the bladder giving you the impression it is full when in fact it is not.
SENSE OF SMELL AND TASTE:
Food and drink will start to taste different as your sense of taste (and therefore smell also) is changed. This will lead to a change in likes and dislikes of certain foods. Food which was previously disagreeable may now be quite appealing and favorite food and drink maybe disliked during the whole of the pregnancy. Certain foods will produce queasiness and other foods will be craved for.
(Source : http://pregnantaid.com)