It sounds like you might have a kidney stone. Back pain is common in late pregnancy, but it isn't a symptom of early pregnancy. I'd call the doc and get checked out -
Im going to the doc tomorrow for a blood test to sed if im pregnant. IF i am im probably about 8 weeks also, and ive been having crazy lower back pain the past 3 days. Which ill let u know if i end up pregnant, if its a symptom of that or not. But im hoping! Con grats and good luck'