Help Ladies!

So today I had my first Dr appt. Did not get an ultrasound done due to the Dr being busy . But my concern is going off of my last period I should be 7 weeks, the Dr measured my uterus and said that according to the feeling I am about 8 - 9 weeks! Has anyone had this situation before? Is the uterus measuring bigger because of twins? And help is appreciated ladies, thanks!