Okay...Only ONLY follow the opinion of your doctor or the technicians when determining gender. How high or low you carry is ~NOT~ determined by the sex of the baby, but the way your body is constructed and how your hips and uterus are cradling the baby.
HOWEVER, on that note, sometimes mistakes are made by the technicians, and they decide that the baby is a girl because of an absence of a clear penis on the screen..or mistakenly say it's a boy when it happens to be part of the cord they scanned. I would keep your purchasing paperwork from stores, but, if you've been told it's a girl, and you STRONGLY feel the baby is a she, chances are good the baby is a girl. Most good technicians and doctors won't give you a gender for certain unless they get a really good view of the genitals. Usually, they'll state 'it looks like' or 'I think it's'...if they can point and say 'see that? That means...' Just ask, and if they don't want to say, explain and usually they'll try to find out.
Best of luck!
Sixth pregnancy, mom of twins.