Back pain is something I've suffered with since before my pregnancy with Lily. I first started noticing it at the end of long uni days after carrying around bags full of books or whilst attempting to walk back to my student digs with my mountains of bags full of food shopping.
Not long after I first started noticing the back pain I actually found out I was pregnant with Lily and from there on it just worsened until it got to the point where I was heavily pregnant and could barely move by the end of the day because of the pain in my back. Back pain affects pregnant woman in particular and a study from Deep Freeze has shown that out of 36% of pregnant woman who choose not to exercise in pregnancy, 20% choose not to specifically due to their back pain. This doesn't surprise me at all actually.
For me, the back pain never went away even after giving birth and the pain would be exacerbated by picking up Lily for long periods of time which I always found incredibly frustrating and less than ideal when you have a baby's needs to attend to.