Same thing happens to me, lol.
I was thinking it might be her head lol cuz after the annoying pain is gone it feels to me like she's pushing against me right there afterwards or right before it happens. But i haven't felt it since a couple minutes after I posted the question.
I'm due in 13 days and have been getting these for a week or so... I've been told that it's he baby's head engaging and preparing for labour and that it's nothing to worry about but I would ring up your midwife to be sure... Good luck!
It could be our bodies getting prepared for labor..
I get it to, it doesn't last long and it doesn't reall hurt.. idk what it is "/ should call and ask. Mines don't really come that often, maybe once or twice then it'll go away...