It is common for women to experience backache during early pregnancy, including at 4 weeks. This discomfort can be caused by hormonal changes, ligament stretching, and the shifting of your center of gravity as your uterus grows. However, if the pain is severe or accompanied by other symptoms such as bleeding or cramping, it is important to consult with your healthcare provider to rule out any underlying issues. To alleviate mild backaches, you can try using heat packs, practicing good posture, doing gentle exercises recommended by your doctor, and wearing supportive shoes. If the pain persists or worsens, seek medical advice for further evaluation and guidance.