During the third week of pregnancy, you may experience several common symptoms. These can include implantation bleeding, breast tenderness, fatigue, and mild cramping. Some women may also notice changes in their cervical mucus or an increased sense of smell. It's important to note that not all women will experience these symptoms, and they can vary from person to person. If you suspect you may be pregnant, it's always best to take a home pregnancy test or consult with your healthcare provider for confirmation.