Pregnancy usually takes about two to three weeks after sex to occur. Pregnancy begins when a fertilized egg attaches to the wall of the uterus, and symptoms may start in some people as early as a week after this occurs. Other people may have no signs other than a missed period until a few months into the pregnancy.
The only way to know for sure if you are pregnant is to take a pregnancy test.
What Are Common Pregnancy Symptoms?
In many women, a missed period is the first sign of pregnancy.
Common pregnancy symptoms include:
- Implantation bleeding
- Occurs when a 6 to 12-day-old fertilized egg attaches to the inner lining of the uterus, resulting in light vaginal bleeding or spotting
- Bleeding is light pinkish or brownish – usually slightly different in color than a woman’s normal menstrual period
- Usually happens near the time of a woman’s next expected menstrual period
- Only lasts 1 to 3 days
- Not all women will have this symptom
- Nausea/morning sickness
- Vomiting
- Tiredness/fatigue
- Tender or swollen breasts
- Headaches
- Frequent urination
- Backaches
- Can occur in early pregnancy but are more common later, during weeks 27 to 34
- Food cravings or food aversions
- Darkening of the area around the nipple (areolas)
- Mood swings caused by hormonal changes
From 
Pregnancy and Parenting Resources
References