Question about ultrasounds during pregnancy!

Okay so I had my first ultrasound at 9 weeks, baby was perfect. I had to switch OB doctors because my previous OB was a hour away from where I lived, so generally we want a doctor closer for when baby time comes. I see the new OB January 7th. When I made the appointment she said I'd get a ultrasound and whatnot so I was pretty excited. Until they call today and told me since I had my first ultrasound at 9 weeks with my previous OB that they will not give me one until 18 to 20 weeks. I am only at 13 weeks, but I am curious if this is normal. I even asked if I could request for one anyways and she told me unless I have a medical reason I can not request. She later calls and says they will do a hand held ultrasound to check the heartrate and i can see the baby on that. To me i dont see much of a difference in either one, the bigger one you get pictures the small one you dont. I just feel as a first time mommy and not knowing if there is any medical issues to be concerned about that you think they would want to also check the development since this is the first time they will see me. I'm just curious if this is normal, I've read that normally they only do 2 ultrasounds per pregnancy, but I have noticed many women on here and people I know who have gotten over that. I just dont want to jerked around by doctors.