Ultrasound Question.

Okay I'm 17 and pregnant and I went for my first ultrasound a couple if days ago and going by my last period I am 10 weeks and 2 days (At the time of the ultrasound). My soon to be mother-in-law showed the ultrasound to a family friend that is a RN (registered nurse) and a former ultrasound tech for 20+ years and she said the baby looks to be more like 12 weeks. Could this be possible?