Very normal. Your body produces a hormone that helps relaxes your ligaments. This helps your uterus grow normally. Unfortunalely the hormone (relaxine) has action on all ligaments, not just those around the uterus, resulting in back pain and more or less everywhere pain. Good luck, i have been in pain since week 3 and am now in week 12, and it's not getting any better, so seriously good luck, hope it will pass quickly for you...