I had the same problem. My baby's legs were crossed and my doc. wouldn't give me another u/s. Then, when I was at 36 weeks, my doc wanted me to see one of the other docs incase he wasn't on call when I went into labor. The other doctor instantly asked me if I wanted to know the sex. Of course I did!
Before I had the u/s, he said he would put money on a girl because I was due in July. Well, he did the u/s and sure enough, it was a girl!
BTW-my doctor told me I was probably having a boy because the heart rate was always 130-something. It's NOT TRUE.