When will I have ultrasound again?

Lisa • Pregnant with our first baby boy 💙 due sept. 14, 2015. 👼
Hey ladies, 
I haven't had an ultrasound for quite some time. I'm 31 weeks and for the past 5 doctors appointments or so, they just check my baby's heartbeat. Do you know when you get an ultrasound again or do the doctors not do one? I'm guessing they have to do it coming up here to check the placement of the baby or am I wrong?