I was told by a stand in midwife at 33 weeks that the baby was B2B. She actually said "ooh, I wouldn't be sitting down much if I was you" (not very helpful really)
I swam, walked, bounced, spent time on all fours, adjusted my work chair, put a cushion in the car, lay in the correct position etc - you name it, I did it (apart from the hanging off the bed upside down thing - I couldn't manage that!)
Basically I was uncomfortable, couldn't relax and it was on my mind pretty much constantly.
I then saw my midwife 2 weeks later and the baby had turned, which I was pleased about, but she also said to me that there are studies that show that babies who are delivered B2B aren't actually mostly in a B2B position in the womb before birth but they turn backwards last minute before delivery.
Also, babies who are B2B prior to labour quite often turn the right way last minute.
She also said it wasn't a good thing that I'd been made to worry about it so early when there was plenty of time left.
I don't honestly know what's true - but I would definitely say read up on it, and consider your general sitting posture, spending some time on the ball etc - I liked the ball anyway. But please don't let it worry you and don't stop yourself being comfortable. It's better to get good sleeps and be able to relax comfortably if you can.