Well, I had a sciatic nerve issue many years back. It went from hip down my leg, sometimes my back would hurt too. Sometimes my baby will sit on it and there it goes... Pain until she moves again.
I'm hoping for your sake its nothing with your kidneys, infection or stone or otherwise. My friend had to pass stones only a week before giving birth back in December. Its very unpleasant and unfortunately more painful than childbirth is what she and many others have said.
They can test urine for signs of infection I think, ultrasound for stones, and if it's just the nerve you just have to deal with it until baby moves off it.
Yes i have had the same semptoms and i have no clie why its happening and it really really hurts please help if anybody knows why please