I had my ultrasound 2 1/2 weeks ago kinda unsure of ?

I went to my ultrasound with an empty bladder I drank a large drink from McD on the way there but it didn't make its way to my bladder. She told me that she couldn't get a good picture of my baby she had to wiggle my belly and tilt me upside down. She also said I might have to do another ultrasound if what pictures she did get weren't good enough. But she did say that the baby looks like a boy. I'm a little unsure if I want to go with that I just don't want to buy all the baby clothes and out comes a girl. Do you think she's right or should I ask for another ultrasound. I was also at 19 weeks of my pregnancy.