Ultrasounds with high-risk pregnancies

OK so I have a question, this is my first pregnancy ever. So I am unaware with how things are supposed to happen at the doctors office. I've been to the doctor two times since I've been pregnant. I found out I was pregnant in August and they made my first doctors appointment for September so I was exactly 5 weeks when I got the ultrasound. I went back to the gynecologist at nine weeks for the heartbeat and I will be returning to the doctors office at 16 weeks for my second ultrasound. A lot of my friends said that's unusual and that they have gotten more ultrasounds or more visits with their doctor. I am also on high risk pregnancy for having a preemie. I wasn't supposed ever be able to get pregnant or anything. Does all of this sound right? I'm concerned because I heard when you're on high-risk pregnancy they're supposed to be a lot more appointments to make sure the baby is OK and developing OK. Can anybody help me?