Ovulated late or on time??

Brianna

So according to my last visit ultrasound measurements I am about 2 weeks behind what my ovulation says. So I am almost 12 weeks but my belly is so big for how far along I am according to ultra sound. So what are my chances that I am right on track and it just looked smaller with the first ultrasound? Any mommas thoughts?

Note: this will be my 3rd baby