In pregnancy why back hurt so much what to do for relief ?

Weight of baby: The weight of the baby, amniotic fluid, & enlarged uterus is altering the mechanics of forces on your spine. For that reason, you r probably walking in a different posture & using muscles to stabiize your spine that u are not used to using. All of these problems frequently lead to back pain, which, unfortunately, is all too common in pregnancy. Talk to ur doctor about helpful treatment & exercises