The most commonly noticed sign that you may be pregnant is a missed or 'late' period, which is often followed up by a simple home pregnancy test. While these tests are generally reliable, they are not infallible. They may deliver either a false positive or a false negative result. For final confirmation you need to see your doctor, who can give you a clear answer from around two weeks after ovulation.
There are other factors than pregnancy which can interrupt or delay your menstrual cycle. These include stress, excessive exercise, low body weight, hormonal imbalances or illness, and if you are still breastfeeding from an earlier pregnancy then your body may not have resumed its normal cycle. Also, bleeding can sometimes continue after pregnancy has begun, so of itself this cannot be relied on as definitive of being pregnant.
Other pregnancy indicators include elevated body temperature, breast changes and darkening of the nipple area, more frequent urination, heightened sensitivity to aromas and odours, food cravings and changes to sense of taste, increased emotional sensitivity, fatigue and need of rest. Between the 4th - 6th week you will very possibly begin to experience some level of morning sickness, which will often continue until around the 12th week.
The full impact of any or all of these effects varies considerably from one person to another, and from one pregnancy to another for the same woman. Morning sickness, for example, may be barely discernable in one pregnancy yet may cause considerable discomfort during another. Similarly the mother-to-be may feel noticably fatiqued during one pregnancy yet maintain adequate vitality and energy during another.
Please note: When you visit a doctor in regard to your pregnancy you need to ensure that you specify any medication you are taking, any other conditions for which you are receiving medical treatment, and any allergies you have experienced.