J.G.
I don't know if it's "normal". But, I had that with my first child... and not to scare you but I had really bad back labor too. It could be just the position of the baby this time. Both my babies were head down but for some reason the first one killed my back the whole last trimester and I ended up having back labor. You may just be having pre-labor pains too. That's what it was for me. It felt like just what you described.