I've had a similar pain for nearly two years now, not very nice if it feels the same. The pain I used to get down my leg has died off now, and for a while it radiated through to my back.
I've been told it's not related to the pill and that if anything the pill would make it better - I am somehow sceptical though as it is worse just before and during my periods.
All the best for finding the cause, I've had 5 ultra sounds a few 'internals' and still no joy

Hope the answer is easier for you

I left it around two months before I went to the doctor, so that they couldn't say it was 'adjustment time', though I probably left it too long being in pain.
Good Luck