3D Sonogram, Dates Wrong??

I had a 3D sonogram on Wednesday, i was 31 weeks 2 days. I did the sonogram just for the fun, not because my doctor ordered it. And i also wouldnt need another 2D sono, because everything was going good during my pregnancy. When we went, the baby was looked so squished in there, and the lady said shes got her head real far down into my pelvis. She also asked when my due date was, as if maybe it could have been wrong. I asked her if she could tell how much she weighed, but she said no, that since my doctor didnt order the sono, she couldnt do it. Also, she couldnt really tell me anything, because it was just entertainment, not for the doctor. My baby looked like her cheeks were really chubby, and all the other 3D sono pictures ive seen when they are around 31 or 32 weeks, their cheeks dont quite look like that, but the pics ive seen around 35 or 36 weeks do. Do you think i could be farther along? I go to the doc on monday, i plan on asking her then, but wanted some advice! Thanks!!