When I was pregnant and went to the doctor the first time my measurements were always bigger than they were supposed to be too, I dont know why ,maybe its just we have bigger uteruses. It may also be a possibility that there is more than one in there did they do a ultrasound? It may still be too soon to know yet. But when mine was bigger they gave me one just to make sure there was only one and there was. I wouldn't be too worried about it. As my pregnancies went on the measurements started to correct themselves.