Most women will have some signs or symptoms of pregnancy within 3 weeks of becoming pregnant. As you mentioned, morning sickness can be one of these symptoms. Other common symptoms include breast tenderness (or a feeling of growth or fullness), increased urination, fatigue, and--of course--missing your period (which is called amenorrhea). In most cases, these symptoms should not begin for the first few days after sex, as the fertilized egg is still in transit to its final resting place (implantation) in the uterus and hormones are just beginning to "ramp up." After this occurs (about 4 days before you would expect to have your period, if you normally have a cycle of 3 to 5 weeks), the amount of the pregnancy hormone hCG doubles every 1 to 2 days. This hormone is what is measured by home pregnancy kits that you can buy over the counter. It is important to note that, even though these tests say that they can detect 99% of pregnancies, the actual number is less than that, and is also dependent on the brand that you use. The best (meaning the most sensitive or earliest) test is the blood test that you can have done in your doctor
's office. It is important to remember that all women of child bearing age are recommended to be taking folate supplements and to avoid smoking. Alcohol consumption is also a bad idea if there is any chance that you might be pregnant. In short, if you think that you might be pregnant, you should be talking to your OB/GYN and your doctors
">primary care doctor for appropriate prenatal care no matter what a pregnancy test says. And, even though no one needs to remind you now, proper barrier protection (eg, condoms) and/or abstinence help with preventing both pregnancy as well as sexually transmitted diseases.