Definitely sounds like your siatic nerve, I suffer from kidney stones and things like that and believe me kidney stones are equal to giving birth on the pain scale. And also I've never had my leg hurt due to kidney stones.
I'm only 4weeks and this is baby number 2 but my first was a breeze it was only at the end I had kidney stones yes it felt like labor the meds they put me on idk if it is working because my right kidney hurts almost all day and I'm scared
It sounds more like your sciatic nerve is being pinched. I don't know how far along you are but my baby will sit on my nerve and I'll have a wonderfully painful time getting about until she moves off it....
I don't believe kidney stones would be able to affect the nerve. You'd best hope for the nerve to be temporarily pinched rather than kidney stones which I've been told by my friends is worse than child birth... Which she had to pass a few days before giving birth.