I had my last ultrasound at 20 weeks. I'm getting a 3D/4D one when I'm 31 weeks for fun ( my doc does them for free). So you probably won't get another unless you pay for it.
I would call in and tell them you want o schedule it for around then because depending on the area they can be booked for 3D ultrasounds.
I'm in Oklahoma and it was $150.
How much did the 3D ultrasound cost where you are? I am wanting to get one done when I get close to 30 weeks.
You typically don't have an ultrasound after the gender scan unless the dr thinks there may be an issue. I'm 37 weeks and haven't had one by a dr since 18 weeks. But I did have an elective 3D done at 29 weeks