ultrasound

I have an ultrasound later this week on Friday to be exact because my pregnancy was switched over since I'm high risk. I've been high risk since 22 weeks I believe, but my appointments were 45 to an hour away from where I live so I complained, but they wouldn't do anything until I saw my heart doctor which I did. He cleared me, but I'm still high risk considering my heart. I'm just wondering why I have a ultrasound so late? I'm 36 weeks and my last one was 20 weeks and I'm just wondering when I go if I can get a 3D ultrasound, I want one so bad. But there's no places near me that do them except a place 2 hours away.