Yes, it is common to experience back pain and constipation during the 5th week of pregnancy. Back pain can be caused by hormonal changes, ligament stretching, or increased pressure on the spine due to a growing uterus. Constipation is also a common symptom due to hormonal changes that slow down digestion and the pressure exerted by the expanding uterus on the intestines. To alleviate these symptoms, you can try gentle exercises, maintain good posture, drink plenty of water, eat fiber-rich foods, and consult your healthcare provider for safe remedies or medications if necessary.